Calling method by name.
I know is possible to create an object from its name. It's possible to call a method from that object if the name is only known at runtime? Would something like the following be possible? string classname, methodname; // Ask the user for class and method. auto obj = Object.factory(classname); invoke(methodname, obj, param1, param2); Thanks
Re: Calling method by name.
On 02/02/11 17:55, %u wrote: I know is possible to create an object from its name. It's possible to call a method from that object if the name is only known at runtime? Would something like the following be possible? string classname, methodname; // Ask the user for class and method. auto obj = Object.factory(classname); invoke(methodname, obj, param1, param2); Thanks As far as I'm aware there is no way to do this in any of the standard libraries. This said, it is possible (at least to some extent), to do some runtime reflection by parsing symbols out of the object file and demangling them - this is what I'm using, but it's not as extensive as what you're requesting, it's very use specific (mainly missing calling methods with any number of parameters). It should be possible with some work though. -- Robert http://octarineparrot.com/
Re: Calling method by name.
On 2011-02-02 20:42, Robert Clipsham wrote: On 02/02/11 17:55, %u wrote: I know is possible to create an object from its name. It's possible to call a method from that object if the name is only known at runtime? Would something like the following be possible? string classname, methodname; // Ask the user for class and method. auto obj = Object.factory(classname); invoke(methodname, obj, param1, param2); Thanks As far as I'm aware there is no way to do this in any of the standard libraries. This said, it is possible (at least to some extent), to do some runtime reflection by parsing symbols out of the object file and demangling them - this is what I'm using, but it's not as extensive as what you're requesting, it's very use specific (mainly missing calling methods with any number of parameters). It should be possible with some work though. Another possibility would be to using __traits with some allMembers, collecting all the names and a delegate in a hash and store it in the object. -- /Jacob Carlborg
Re: Calling method by name.
On 02/02/11 20:00, Jacob Carlborg wrote: On 2011-02-02 20:42, Robert Clipsham wrote: On 02/02/11 17:55, %u wrote: I know is possible to create an object from its name. It's possible to call a method from that object if the name is only known at runtime? Would something like the following be possible? string classname, methodname; // Ask the user for class and method. auto obj = Object.factory(classname); invoke(methodname, obj, param1, param2); Thanks As far as I'm aware there is no way to do this in any of the standard libraries. This said, it is possible (at least to some extent), to do some runtime reflection by parsing symbols out of the object file and demangling them - this is what I'm using, but it's not as extensive as what you're requesting, it's very use specific (mainly missing calling methods with any number of parameters). It should be possible with some work though. Another possibility would be to using __traits with some allMembers, collecting all the names and a delegate in a hash and store it in the object. If it's possible to do this, you should, it's what I'd be using if I had access to it, unfortunately, there's no such love for D1. -- Robert http://octarineparrot.com/
Re: Calling method by name.
On 02/02/2011 11:11 PM, Robert Clipsham wrote: On 02/02/11 20:00, Jacob Carlborg wrote: On 2011-02-02 20:42, Robert Clipsham wrote: On 02/02/11 17:55, %u wrote: I know is possible to create an object from its name. It's possible to call a method from that object if the name is only known at runtime? Would something like the following be possible? string classname, methodname; // Ask the user for class and method. auto obj = Object.factory(classname); invoke(methodname, obj, param1, param2); Thanks As far as I'm aware there is no way to do this in any of the standard libraries. This said, it is possible (at least to some extent), to do some runtime reflection by parsing symbols out of the object file and demangling them - this is what I'm using, but it's not as extensive as what you're requesting, it's very use specific (mainly missing calling methods with any number of parameters). It should be possible with some work though. Another possibility would be to using __traits with some allMembers, collecting all the names and a delegate in a hash and store it in the object. If it's possible to do this, you should, it's what I'd be using if I had access to it, unfortunately, there's no such love for D1. AFAIK, D2's TypeInfo and friends do have an interface for runtime reflection (methods offTi() and getMembers()), though a quick glance shows they're not implemented, i.e. return null all the time.
Re: Calling method by name.
On 2/2/11, Stanislav Blinov wrote: > AFAIK, D2's TypeInfo and friends do have an interface for runtime > reflection (methods offTi() and getMembers()), though a quick glance > shows they're not implemented, i.e. return null all the time. > Talk about posting this after I've spent 20 minutes trying to figure out why getMembers doesn't work!
Re: Calling method by name.
On Wed, 02 Feb 2011 12:55:37 -0500, %u wrote:
I know is possible to create an object from its name. It's possible to
call a method from that object if the name is only known at runtime?
Would something like the following be possible?
string classname, methodname;
// Ask the user for class and method.
auto obj = Object.factory(classname);
invoke(methodname, obj, param1, param2);
Thanks
I've been working on an update to std.variant, which includes a
compile-time reflection to runtime-reflection system. (See
https://jshare.johnshopkins.edu/rjacque2/public_html/) From the docs:
Manually registers a class with Variant's runtime-reflection system. Note
that Variant automatically registers any types it is exposed. Note how in
the example below, only Student is manually registered; Grade is
automatically registered by Variant via compile-time reflection of Student.
module example;
class Grade { real mark; }
class Student { Grade grade; }
void main(string[] args) {
Variant.__register!Student;
Variant grade = Object.factory("example.Grade");
grade.mark(96.6);
assert(grade.mark == 96.6);
}
And dynamic method/field calls are handled via the __reflect(string name,
Variant[] args...) method like so:
grade.__reflect("mark",Variant(96.6));
assert(grade.__reflect("mark") == 96.6);
Re: Calling method by name.
On 2011-02-02 21:11, Robert Clipsham wrote: On 02/02/11 20:00, Jacob Carlborg wrote: On 2011-02-02 20:42, Robert Clipsham wrote: On 02/02/11 17:55, %u wrote: I know is possible to create an object from its name. It's possible to call a method from that object if the name is only known at runtime? Would something like the following be possible? string classname, methodname; // Ask the user for class and method. auto obj = Object.factory(classname); invoke(methodname, obj, param1, param2); Thanks As far as I'm aware there is no way to do this in any of the standard libraries. This said, it is possible (at least to some extent), to do some runtime reflection by parsing symbols out of the object file and demangling them - this is what I'm using, but it's not as extensive as what you're requesting, it's very use specific (mainly missing calling methods with any number of parameters). It should be possible with some work though. Another possibility would be to using __traits with some allMembers, collecting all the names and a delegate in a hash and store it in the object. If it's possible to do this, you should, it's what I'd be using if I had access to it, unfortunately, there's no such love for D1. Same here, but you would probably need to inherit from a common base class or use a mixin. -- /Jacob Carlborg
Re: Calling method by name.
On 2011-02-02 22:51, Stanislav Blinov wrote: On 02/02/2011 11:11 PM, Robert Clipsham wrote: On 02/02/11 20:00, Jacob Carlborg wrote: On 2011-02-02 20:42, Robert Clipsham wrote: On 02/02/11 17:55, %u wrote: I know is possible to create an object from its name. It's possible to call a method from that object if the name is only known at runtime? Would something like the following be possible? string classname, methodname; // Ask the user for class and method. auto obj = Object.factory(classname); invoke(methodname, obj, param1, param2); Thanks As far as I'm aware there is no way to do this in any of the standard libraries. This said, it is possible (at least to some extent), to do some runtime reflection by parsing symbols out of the object file and demangling them - this is what I'm using, but it's not as extensive as what you're requesting, it's very use specific (mainly missing calling methods with any number of parameters). It should be possible with some work though. Another possibility would be to using __traits with some allMembers, collecting all the names and a delegate in a hash and store it in the object. If it's possible to do this, you should, it's what I'd be using if I had access to it, unfortunately, there's no such love for D1. AFAIK, D2's TypeInfo and friends do have an interface for runtime reflection (methods offTi() and getMembers()), though a quick glance shows they're not implemented, i.e. return null all the time. I think the const is incorrect as well on getMembers. -- /Jacob Carlborg
Re: Calling method by name.
03.02.2011 12:54, Jacob Carlborg пишет: On 2011-02-02 22:51, Stanislav Blinov wrote: AFAIK, D2's TypeInfo and friends do have an interface for runtime reflection (methods offTi() and getMembers()), though a quick glance shows they're not implemented, i.e. return null all the time. I think the const is incorrect as well on getMembers. Actually, it's that those TypeInfo, MemberInfo et al. are not const-correct, as is the case for Object and other Object-related classes.
Re: Calling method by name.
On 2011-02-03 05:52, Robert Jacques wrote:
On Wed, 02 Feb 2011 12:55:37 -0500, %u wrote:
I know is possible to create an object from its name. It's possible to
call a method from that object if the name is only known at runtime?
Would something like the following be possible?
string classname, methodname;
// Ask the user for class and method.
auto obj = Object.factory(classname);
invoke(methodname, obj, param1, param2);
Thanks
I've been working on an update to std.variant, which includes a
compile-time reflection to runtime-reflection system. (See
https://jshare.johnshopkins.edu/rjacque2/public_html/) From the docs:
Manually registers a class with Variant's runtime-reflection system.
Note that Variant automatically registers any types it is exposed. Note
how in the example below, only Student is manually registered; Grade is
automatically registered by Variant via compile-time reflection of Student.
module example;
class Grade { real mark; }
class Student { Grade grade; }
void main(string[] args) {
Variant.__register!Student;
Variant grade = Object.factory("example.Grade");
grade.mark(96.6);
assert(grade.mark == 96.6);
}
And dynamic method/field calls are handled via the __reflect(string
name, Variant[] args...) method like so:
grade.__reflect("mark",Variant(96.6));
assert(grade.__reflect("mark") == 96.6);
Why would you need to pass in Variants in __reflect? Why not just make
it a variadic method and automatically convert to Variant?
--
/Jacob Carlborg
Re: Calling method by name.
On Thu, 03 Feb 2011 08:49:54 -0500, Jacob Carlborg wrote:
On 2011-02-03 05:52, Robert Jacques wrote:
On Wed, 02 Feb 2011 12:55:37 -0500, %u wrote:
I know is possible to create an object from its name. It's possible to
call a method from that object if the name is only known at runtime?
Would something like the following be possible?
string classname, methodname;
// Ask the user for class and method.
auto obj = Object.factory(classname);
invoke(methodname, obj, param1, param2);
Thanks
I've been working on an update to std.variant, which includes a
compile-time reflection to runtime-reflection system. (See
https://jshare.johnshopkins.edu/rjacque2/public_html/) From the docs:
Manually registers a class with Variant's runtime-reflection system.
Note that Variant automatically registers any types it is exposed. Note
how in the example below, only Student is manually registered; Grade is
automatically registered by Variant via compile-time reflection of
Student.
module example;
class Grade { real mark; }
class Student { Grade grade; }
void main(string[] args) {
Variant.__register!Student;
Variant grade = Object.factory("example.Grade");
grade.mark(96.6);
assert(grade.mark == 96.6);
}
And dynamic method/field calls are handled via the __reflect(string
name, Variant[] args...) method like so:
grade.__reflect("mark",Variant(96.6));
assert(grade.__reflect("mark") == 96.6);
Why would you need to pass in Variants in __reflect? Why not just make
it a variadic method and automatically convert to Variant?
Well, opDispatch does exactly that. __reflect, on the other hand, was
designed as a quasi-backend function primarily for a) internal use (hence
the double underscore), b) scripting language interfacing/implementing and
c) user-extension. So efficiency was of key importance. And the reflection
system is extensible, as Variant knows to call __reflect on user defined
types. This makes things like prototype style objects possible. (There's
even a beta implementation of a prototype object in the library) But this
requires that the use __reflect methods not be templated.
I'm not well versed in dynamic reflection and its use cases, so when I
considered the combination of a runtime method name and compile-time
argument type information, I classed it as 'rare in practice'. But if
that's not the case, I'd like to know and would greatly appreciate a use
case/unit test.
Re: Calling method by name.
On Thursday 03 February 2011 19:29:15 Robert Jacques wrote:
> On Thu, 03 Feb 2011 08:49:54 -0500, Jacob Carlborg wrote:
> > On 2011-02-03 05:52, Robert Jacques wrote:
> >> On Wed, 02 Feb 2011 12:55:37 -0500, %u wrote:
> >>> I know is possible to create an object from its name. It's possible to
> >>> call a method from that object if the name is only known at runtime?
> >>>
> >>> Would something like the following be possible?
> >>>
> >>> string classname, methodname;
> >>> // Ask the user for class and method.
> >>> auto obj = Object.factory(classname);
> >>> invoke(methodname, obj, param1, param2);
> >>>
> >>> Thanks
> >>
> >> I've been working on an update to std.variant, which includes a
> >> compile-time reflection to runtime-reflection system. (See
> >> https://jshare.johnshopkins.edu/rjacque2/public_html/) From the docs:
> >>
> >> Manually registers a class with Variant's runtime-reflection system.
> >> Note that Variant automatically registers any types it is exposed. Note
> >> how in the example below, only Student is manually registered; Grade is
> >> automatically registered by Variant via compile-time reflection of
> >> Student.
> >>
> >> module example;
> >> class Grade { real mark; }
> >> class Student { Grade grade; }
> >> void main(string[] args) {
> >> Variant.__register!Student;
> >> Variant grade = Object.factory("example.Grade");
> >> grade.mark(96.6);
> >> assert(grade.mark == 96.6);
> >> }
> >>
> >> And dynamic method/field calls are handled via the __reflect(string
> >> name, Variant[] args...) method like so:
> >>
> >> grade.__reflect("mark",Variant(96.6));
> >> assert(grade.__reflect("mark") == 96.6);
> >
> > Why would you need to pass in Variants in __reflect? Why not just make
> > it a variadic method and automatically convert to Variant?
>
> Well, opDispatch does exactly that. __reflect, on the other hand, was
> designed as a quasi-backend function primarily for a) internal use (hence
> the double underscore), b) scripting language interfacing/implementing and
> c) user-extension. So efficiency was of key importance. And the reflection
> system is extensible, as Variant knows to call __reflect on user defined
> types. This makes things like prototype style objects possible. (There's
> even a beta implementation of a prototype object in the library) But this
> requires that the use __reflect methods not be templated.
>
> I'm not well versed in dynamic reflection and its use cases, so when I
> considered the combination of a runtime method name and compile-time
> argument type information, I classed it as 'rare in practice'. But if
> that's not the case, I'd like to know and would greatly appreciate a use
> case/unit test.
Most of the good examples of runtime reflection that I'm aware of require user-
defined attributes. But there are libraries in Java (and presumably C#) that do
stuff like allow you to mark your classes with certain attributes indicating
what
type of XML elements that they should be, and then another library which knows
_nothing_ about your classes is able to serialize them to and from XML. Another
example would be Hibernate, which does the same sort of stuff only it deals
with
talking to databases. Full-on runtime reflection combined with user-defined
attributes can do some powerful stuff. However, I do think that runtime
reflection
without user-defined attributes doesn't tend to be anywhere near as useful. To
really get that sort of stuff working, we'd need D to properly support both
user-
defined attributes and runtime reflection. Both are future possibilities but
obviously aren't happening any time soon.
- Jonathan M Davis
Re: Calling method by name.
On Thu, Feb 3, 2011 at 10:07 PM, Jonathan M Davis wrote:
> On Thursday 03 February 2011 19:29:15 Robert Jacques wrote:
> > On Thu, 03 Feb 2011 08:49:54 -0500, Jacob Carlborg wrote:
> > > On 2011-02-03 05:52, Robert Jacques wrote:
> > >> On Wed, 02 Feb 2011 12:55:37 -0500, %u wrote:
> > >>> I know is possible to create an object from its name. It's possible
> to
> > >>> call a method from that object if the name is only known at runtime?
> > >>>
> > >>> Would something like the following be possible?
> > >>>
> > >>> string classname, methodname;
> > >>> // Ask the user for class and method.
> > >>> auto obj = Object.factory(classname);
> > >>> invoke(methodname, obj, param1, param2);
> > >>>
> > >>> Thanks
> > >>
> > >> I've been working on an update to std.variant, which includes a
> > >> compile-time reflection to runtime-reflection system. (See
> > >> https://jshare.johnshopkins.edu/rjacque2/public_html/) From the docs:
> > >>
> > >> Manually registers a class with Variant's runtime-reflection system.
> > >> Note that Variant automatically registers any types it is exposed.
> Note
> > >> how in the example below, only Student is manually registered; Grade
> is
> > >> automatically registered by Variant via compile-time reflection of
> > >> Student.
> > >>
> > >> module example;
> > >> class Grade { real mark; }
> > >> class Student { Grade grade; }
> > >> void main(string[] args) {
> > >> Variant.__register!Student;
> > >> Variant grade = Object.factory("example.Grade");
> > >> grade.mark(96.6);
> > >> assert(grade.mark == 96.6);
> > >> }
> > >>
> > >> And dynamic method/field calls are handled via the __reflect(string
> > >> name, Variant[] args...) method like so:
> > >>
> > >> grade.__reflect("mark",Variant(96.6));
> > >> assert(grade.__reflect("mark") == 96.6);
> > >
> > > Why would you need to pass in Variants in __reflect? Why not just make
> > > it a variadic method and automatically convert to Variant?
> >
> > Well, opDispatch does exactly that. __reflect, on the other hand, was
> > designed as a quasi-backend function primarily for a) internal use (hence
> > the double underscore), b) scripting language interfacing/implementing
> and
> > c) user-extension. So efficiency was of key importance. And the
> reflection
> > system is extensible, as Variant knows to call __reflect on user defined
> > types. This makes things like prototype style objects possible. (There's
> > even a beta implementation of a prototype object in the library) But this
> > requires that the use __reflect methods not be templated.
> >
> > I'm not well versed in dynamic reflection and its use cases, so when I
> > considered the combination of a runtime method name and compile-time
> > argument type information, I classed it as 'rare in practice'. But if
> > that's not the case, I'd like to know and would greatly appreciate a use
> > case/unit test.
>
> Most of the good examples of runtime reflection that I'm aware of require
> user-
> defined attributes. But there are libraries in Java (and presumably C#)
> that do
> stuff like allow you to mark your classes with certain attributes
> indicating what
> type of XML elements that they should be, and then another library which
> knows
> _nothing_ about your classes is able to serialize them to and from XML.
> Another
> example would be Hibernate, which does the same sort of stuff only it deals
> with
> talking to databases. Full-on runtime reflection combined with user-defined
> attributes can do some powerful stuff. However, I do think that runtime
> reflection
> without user-defined attributes doesn't tend to be anywhere near as useful.
> To
> really get that sort of stuff working, we'd need D to properly support both
> user-
> defined attributes and runtime reflection. Both are future possibilities
> but
> obviously aren't happening any time soon.
I would argue that if user-defined attributes could be implemented and tied
into the existing compile time reflection system, we could reap similar
benefits. One popular pattern in the serialization libraries you describe is
that, for performance reasons, runtime reflection can be abandoned in favor
of runtime code generation, where the same reflection system is used once to
dynamically write code that can be used repeatedly. D has the advantage that
such code can be written at compile time.
True, runtime reflection would make this sort of thing more clean and
decoupled, but even using compile time reflection, quite a bit is feasible
if user-defined attributes are defined.
Re: Calling method by name.
On Thursday 03 February 2011 20:23:25 Andrew Wiley wrote:
> On Thu, Feb 3, 2011 at 10:07 PM, Jonathan M Davis wrote:
> > On Thursday 03 February 2011 19:29:15 Robert Jacques wrote:
> > > On Thu, 03 Feb 2011 08:49:54 -0500, Jacob Carlborg wrote:
> > > > On 2011-02-03 05:52, Robert Jacques wrote:
> > > >> On Wed, 02 Feb 2011 12:55:37 -0500, %u wrote:
> > > >>> I know is possible to create an object from its name. It's possible
> >
> > to
> >
> > > >>> call a method from that object if the name is only known at
> > > >>> runtime?
> > > >>>
> > > >>> Would something like the following be possible?
> > > >>>
> > > >>> string classname, methodname;
> > > >>> // Ask the user for class and method.
> > > >>> auto obj = Object.factory(classname);
> > > >>> invoke(methodname, obj, param1, param2);
> > > >>>
> > > >>> Thanks
> > > >>
> > > >> I've been working on an update to std.variant, which includes a
> > > >> compile-time reflection to runtime-reflection system. (See
> > > >> https://jshare.johnshopkins.edu/rjacque2/public_html/) From the
> > > >> docs:
> > > >>
> > > >> Manually registers a class with Variant's runtime-reflection system.
> > > >> Note that Variant automatically registers any types it is exposed.
> >
> > Note
> >
> > > >> how in the example below, only Student is manually registered; Grade
> >
> > is
> >
> > > >> automatically registered by Variant via compile-time reflection of
> > > >> Student.
> > > >>
> > > >> module example;
> > > >> class Grade { real mark; }
> > > >> class Student { Grade grade; }
> > > >> void main(string[] args) {
> > > >> Variant.__register!Student;
> > > >> Variant grade = Object.factory("example.Grade");
> > > >> grade.mark(96.6);
> > > >> assert(grade.mark == 96.6);
> > > >> }
> > > >>
> > > >> And dynamic method/field calls are handled via the __reflect(string
> > > >> name, Variant[] args...) method like so:
> > > >>
> > > >> grade.__reflect("mark",Variant(96.6));
> > > >> assert(grade.__reflect("mark") == 96.6);
> > > >
> > > > Why would you need to pass in Variants in __reflect? Why not just
> > > > make it a variadic method and automatically convert to Variant?
> > >
> > > Well, opDispatch does exactly that. __reflect, on the other hand, was
> > > designed as a quasi-backend function primarily for a) internal use
> > > (hence the double underscore), b) scripting language
> > > interfacing/implementing
> >
> > and
> >
> > > c) user-extension. So efficiency was of key importance. And the
> >
> > reflection
> >
> > > system is extensible, as Variant knows to call __reflect on user
> > > defined types. This makes things like prototype style objects
> > > possible. (There's even a beta implementation of a prototype object in
> > > the library) But this requires that the use __reflect methods not be
> > > templated.
> > >
> > > I'm not well versed in dynamic reflection and its use cases, so when I
> > > considered the combination of a runtime method name and compile-time
> > > argument type information, I classed it as 'rare in practice'. But if
> > > that's not the case, I'd like to know and would greatly appreciate a
> > > use case/unit test.
> >
> > Most of the good examples of runtime reflection that I'm aware of require
> > user-
> > defined attributes. But there are libraries in Java (and presumably C#)
> > that do
> > stuff like allow you to mark your classes with certain attributes
> > indicating what
> > type of XML elements that they should be, and then another library which
> > knows
> > _nothing_ about your classes is able to serialize them to and from XML.
> > Another
> > example would be Hibernate, which does the same sort of stuff only it
> > deals with
> > talking to databases. Full-on runtime reflection combined with
> > user-defined attributes can do some powerful stuff. However, I do think
> > that runtime reflection
> > without user-defined attributes doesn't tend to be anywhere near as
> > useful. To
> > really get that sort of stuff working, we'd need D to properly support
> > both user-
> > defined attributes and runtime reflection. Both are future possibilities
> > but
> > obviously aren't happening any time soon.
>
> I would argue that if user-defined attributes could be implemented and tied
> into the existing compile time reflection system, we could reap similar
> benefits. One popular pattern in the serialization libraries you describe
> is that, for performance reasons, runtime reflection can be abandoned in
> favor of runtime code generation, where the same reflection system is used
> once to dynamically write code that can be used repeatedly. D has the
> advantage that such code can be written at compile time.
> True, runtime reflection would make this sort of thing more clean and
> decoupled, but even using compile time reflection, quite a bit is feasible
> if user-defined attributes are defined.
I've never really sat down to try and figure out how well compile time
reflection
would work for that sort of thin
Re: Calling method by name.
On 2011-02-04 04:29, Robert Jacques wrote:
On Thu, 03 Feb 2011 08:49:54 -0500, Jacob Carlborg wrote:
On 2011-02-03 05:52, Robert Jacques wrote:
On Wed, 02 Feb 2011 12:55:37 -0500, %u wrote:
I know is possible to create an object from its name. It's possible to
call a method from that object if the name is only known at runtime?
Would something like the following be possible?
string classname, methodname;
// Ask the user for class and method.
auto obj = Object.factory(classname);
invoke(methodname, obj, param1, param2);
Thanks
I've been working on an update to std.variant, which includes a
compile-time reflection to runtime-reflection system. (See
https://jshare.johnshopkins.edu/rjacque2/public_html/) From the docs:
Manually registers a class with Variant's runtime-reflection system.
Note that Variant automatically registers any types it is exposed. Note
how in the example below, only Student is manually registered; Grade is
automatically registered by Variant via compile-time reflection of
Student.
module example;
class Grade { real mark; }
class Student { Grade grade; }
void main(string[] args) {
Variant.__register!Student;
Variant grade = Object.factory("example.Grade");
grade.mark(96.6);
assert(grade.mark == 96.6);
}
And dynamic method/field calls are handled via the __reflect(string
name, Variant[] args...) method like so:
grade.__reflect("mark",Variant(96.6));
assert(grade.__reflect("mark") == 96.6);
Why would you need to pass in Variants in __reflect? Why not just make
it a variadic method and automatically convert to Variant?
Well, opDispatch does exactly that. __reflect, on the other hand, was
designed as a quasi-backend function primarily for a) internal use
(hence the double underscore), b) scripting language
interfacing/implementing and c) user-extension. So efficiency was of key
importance. And the reflection system is extensible, as Variant knows to
call __reflect on user defined types. This makes things like prototype
style objects possible. (There's even a beta implementation of a
prototype object in the library) But this requires that the use
__reflect methods not be templated.
I'm not well versed in dynamic reflection and its use cases, so when I
considered the combination of a runtime method name and compile-time
argument type information, I classed it as 'rare in practice'. But if
that's not the case, I'd like to know and would greatly appreciate a use
case/unit test.
I recommend looking at Ruby, it has very good support for runtime
reflection. ActiveRecord in Rails is hevaly based on runtime reflection.
For example, given the following Ruby class:
class Post < ActiveRecord::Base
end
The class "Post" maps to the database table "posts", no configuration is
necessary. Then you can use the column names in the table as fields to
set and get data, like this:
post = Post.new
post.title = "some title"
post.body = "the body"
post.save # will update the database
All this is done using runtime reflection. Then you can query the
database, also using runtime reflection:
Post.find_by_name_and_body("some title", "the body")
Will find the first row where "title" and "body" matches the given values.
--
/Jacob Carlborg
Re: Calling method by name.
Jacob Carlborg wrote:
> The class "Post" maps to the database table "posts", no configuration is
> necessary. Then you can use the column names in the table as fields to
> set and get data, like this:
>
> post = Post.new
> post.title = "some title"
> post.body = "the body"
> post.save # will update the database
Note that you can do this kind of thing with D's compile time
reflection and CTFE as well. That particular example works
in my own DataObject class (except I called it "commitChanges"
instead of "save").
Some of the stuff is just dynamic; just sugar around a string[string].
Most my own use of "runtime reflection" is just having some CTFE
go through and put the compile time info into those strings which
are used at runtime.
I do that for calling functions by name too, but mine does rely
upon some static info that probably isn't available to the OP.
For example for both, my new newsreader does both:
http://arsdnet.net/d-web-site/nntp/get-message
That screen is automatically generated by this prototype:
Post getMessage(string newsgroup, string messageId) {
The name of the function and arguments in the URL are pulled from
that single line of code. It uses the types of the arguments to
automatically generate an appropriate form.
The way I did it was to put all the public functions in a static
struct. Then, I mixin a template (called FancyMain!(methodStruct))
which scans the struct and generates the needed hashmaps and
delegates to call its methods by name.
http://arsdnet.net/d-web-site/arsd/web.d
That code is very ugly... but look at the prepareReflection and
generateWrapper functions.
Re: Calling method by name.
On 02/04/2011 04:33 PM, Jacob Carlborg wrote:
On 2011-02-04 04:29, Robert Jacques wrote:
On Thu, 03 Feb 2011 08:49:54 -0500, Jacob Carlborg wrote:
Well, opDispatch does exactly that. __reflect, on the other hand, was
designed as a quasi-backend function primarily for a) internal use
(hence the double underscore), b) scripting language
interfacing/implementing and c) user-extension. So efficiency was of key
importance. And the reflection system is extensible, as Variant knows to
call __reflect on user defined types. This makes things like prototype
style objects possible. (There's even a beta implementation of a
prototype object in the library) But this requires that the use
__reflect methods not be templated.
I'm not well versed in dynamic reflection and its use cases, so when I
considered the combination of a runtime method name and compile-time
argument type information, I classed it as 'rare in practice'. But if
that's not the case, I'd like to know and would greatly appreciate a use
case/unit test.
I recommend looking at Ruby, it has very good support for runtime reflection.
ActiveRecord in Rails is hevaly based on runtime reflection. For example, given
the following Ruby class:
class Post < ActiveRecord::Base
end
The class "Post" maps to the database table "posts", no configuration is
necessary. Then you can use the column names in the table as fields to set and
get data, like this:
post = Post.new
post.title = "some title"
post.body = "the body"
post.save # will update the database
All this is done using runtime reflection. Then you can query the database,
also using runtime reflection:
Post.find_by_name_and_body("some title", "the body")
Will find the first row where "title" and "body" matches the given values.
FWIW, python example of "Calling method by name" (using no exotic feature):
class C:
def __init__(self, x):
self.x = x
def write (self, thing):
print "%s == %s ? %s" \
%(self.x,thing, self.x==thing)
def runMethodWithArgs (object, name, *args):
method = getattr(object, name)
method(*args)
c= C(1.11)
runMethodWithArgs(c, "write", 2.22)
# --> 1.11 == 2.22 ? False
(Explanations if needed.)
Denis
--
_
vita es estrany
spir.wikidot.com
Re: Calling method by name.
On 2011-02-04 05:07, Jonathan M Davis wrote:
On Thursday 03 February 2011 19:29:15 Robert Jacques wrote:
On Thu, 03 Feb 2011 08:49:54 -0500, Jacob Carlborg wrote:
On 2011-02-03 05:52, Robert Jacques wrote:
On Wed, 02 Feb 2011 12:55:37 -0500, %u wrote:
I know is possible to create an object from its name. It's possible to
call a method from that object if the name is only known at runtime?
Would something like the following be possible?
string classname, methodname;
// Ask the user for class and method.
auto obj = Object.factory(classname);
invoke(methodname, obj, param1, param2);
Thanks
I've been working on an update to std.variant, which includes a
compile-time reflection to runtime-reflection system. (See
https://jshare.johnshopkins.edu/rjacque2/public_html/) From the docs:
Manually registers a class with Variant's runtime-reflection system.
Note that Variant automatically registers any types it is exposed. Note
how in the example below, only Student is manually registered; Grade is
automatically registered by Variant via compile-time reflection of
Student.
module example;
class Grade { real mark; }
class Student { Grade grade; }
void main(string[] args) {
Variant.__register!Student;
Variant grade = Object.factory("example.Grade");
grade.mark(96.6);
assert(grade.mark == 96.6);
}
And dynamic method/field calls are handled via the __reflect(string
name, Variant[] args...) method like so:
grade.__reflect("mark",Variant(96.6));
assert(grade.__reflect("mark") == 96.6);
Why would you need to pass in Variants in __reflect? Why not just make
it a variadic method and automatically convert to Variant?
Well, opDispatch does exactly that. __reflect, on the other hand, was
designed as a quasi-backend function primarily for a) internal use (hence
the double underscore), b) scripting language interfacing/implementing and
c) user-extension. So efficiency was of key importance. And the reflection
system is extensible, as Variant knows to call __reflect on user defined
types. This makes things like prototype style objects possible. (There's
even a beta implementation of a prototype object in the library) But this
requires that the use __reflect methods not be templated.
I'm not well versed in dynamic reflection and its use cases, so when I
considered the combination of a runtime method name and compile-time
argument type information, I classed it as 'rare in practice'. But if
that's not the case, I'd like to know and would greatly appreciate a use
case/unit test.
Most of the good examples of runtime reflection that I'm aware of require user-
defined attributes. But there are libraries in Java (and presumably C#) that do
stuff like allow you to mark your classes with certain attributes indicating
what
type of XML elements that they should be, and then another library which knows
_nothing_ about your classes is able to serialize them to and from XML. Another
example would be Hibernate, which does the same sort of stuff only it deals with
talking to databases. Full-on runtime reflection combined with user-defined
attributes can do some powerful stuff. However, I do think that runtime
reflection
without user-defined attributes doesn't tend to be anywhere near as useful. To
really get that sort of stuff working, we'd need D to properly support both
user-
defined attributes and runtime reflection. Both are future possibilities but
obviously aren't happening any time soon.
- Jonathan M Davis
Ruby seems to get along without any kind of attributes/annotations. But
on the other hand you can call a method in a class declaration and this
will behave much the same as a attribute.
ActiveRecord in Rails is a good example of runtime reflection. Also the
Ruby XML library "builder" is a good example of runtime reflection.
Maybe not acutally runtime reflection but is uses the "method_missing"
method, equivalent to the "opDispatch" method in D, heavily.
http://builder.rubyforge.org/
--
/Jacob Carlborg
Re: Calling method by name.
On 2011-02-04 17:17, Adam Ruppe wrote: Jacob Carlborg wrote: The class "Post" maps to the database table "posts", no configuration is necessary. Then you can use the column names in the table as fields to set and get data, like this: post = Post.new post.title = "some title" post.body = "the body" post.save # will update the database Note that you can do this kind of thing with D's compile time reflection and CTFE as well. That particular example works in my own DataObject class (except I called it "commitChanges" instead of "save"). Yeah, I tried to do the same. But in this case the static type system was kind of in the way of what I wanted to do. This is so much easier with a dynamic type system. -- /Jacob Carlborg
Re: Calling method by name.
On 2011-02-04 20:03, spir wrote:
On 02/04/2011 04:33 PM, Jacob Carlborg wrote:
I recommend looking at Ruby, it has very good support for runtime
reflection.
ActiveRecord in Rails is hevaly based on runtime reflection. For
example, given
the following Ruby class:
class Post < ActiveRecord::Base
end
The class "Post" maps to the database table "posts", no configuration is
necessary. Then you can use the column names in the table as fields to
set and
get data, like this:
post = Post.new
post.title = "some title"
post.body = "the body"
post.save # will update the database
All this is done using runtime reflection. Then you can query the
database,
also using runtime reflection:
Post.find_by_name_and_body("some title", "the body")
Will find the first row where "title" and "body" matches the given
values.
FWIW, python example of "Calling method by name" (using no exotic feature):
class C:
def __init__(self, x):
self.x = x
def write (self, thing):
print "%s == %s ? %s" \
%(self.x,thing, self.x==thing)
def runMethodWithArgs (object, name, *args):
method = getattr(object, name)
method(*args)
c= C(1.11)
runMethodWithArgs(c, "write", 2.22)
# --> 1.11 == 2.22 ? False
(Explanations if needed.)
Denis
Actually I never showed how to do "call by name" in Ruby, just how it
can be used. Ruby has "built in" (not in the language but in the Object
class) support for this:
p Object.new.send(:to_s) # :to_s is a symbol, basically an immutable
lightweight string
The above will print something like: "#"
To implement the "find_by" methods used in my previous examples you
implement the "method_missing" method:
class Foo
def method_missing (method, *args, &block)
p method, args
end
end
Foo.new.bar 3, 4
Will print:
:bar
[3, 4]
--
/Jacob Carlborg
Re: Calling method by name.
On Sat, 05 Feb 2011 13:14:42 -0500, Jacob Carlborg wrote: On 2011-02-04 05:07, Jonathan M Davis wrote: [snip] Most of the good examples of runtime reflection that I'm aware of require user- defined attributes. But there are libraries in Java (and presumably C#) that do stuff like allow you to mark your classes with certain attributes indicating what type of XML elements that they should be, and then another library which knows _nothing_ about your classes is able to serialize them to and from XML. Another example would be Hibernate, which does the same sort of stuff only it deals with talking to databases. Full-on runtime reflection combined with user-defined attributes can do some powerful stuff. However, I do think that runtime reflection without user-defined attributes doesn't tend to be anywhere near as useful. To really get that sort of stuff working, we'd need D to properly support both user- defined attributes and runtime reflection. Both are future possibilities but obviously aren't happening any time soon. - Jonathan M Davis Ruby seems to get along without any kind of attributes/annotations. But on the other hand you can call a method in a class declaration and this will behave much the same as a attribute. ActiveRecord in Rails is a good example of runtime reflection. Also the Ruby XML library "builder" is a good example of runtime reflection. Maybe not acutally runtime reflection but is uses the "method_missing" method, equivalent to the "opDispatch" method in D, heavily. http://builder.rubyforge.org/ I'm still reading up on Ruby, but so far, there are two major difference between serialization in Ruby and in D. First, Ruby isn't a systems programming language with pointers/unions/etc, so serializing all members of a class is generally okay in Ruby but isn't in D. This is the major advantage of annotations: its a fast, simple way of declaring what should and shouldn't be serialized. Second, Ruby's support for serialization creates a back door around its variable protection annotations (i.e. private,package,protected,public). Now, Ruby doesn't actually have user defined annotations as far as I can tell, but methods are always public and variables are always private. I don't believe that a reflection system should bypass encapsulation. The advantage of annotations is that they allow you to declare programmer intent and possibly separate APIs (ala const(T)) for special purposes.
Re: Calling method by name.
On 2011-02-08 05:54, Robert Jacques wrote:
On Sat, 05 Feb 2011 13:14:42 -0500, Jacob Carlborg wrote:
On 2011-02-04 05:07, Jonathan M Davis wrote:
[snip]
Most of the good examples of runtime reflection that I'm aware of
require user-
defined attributes. But there are libraries in Java (and presumably
C#) that do
stuff like allow you to mark your classes with certain attributes
indicating what
type of XML elements that they should be, and then another library
which knows
_nothing_ about your classes is able to serialize them to and from
XML. Another
example would be Hibernate, which does the same sort of stuff only it
deals with
talking to databases. Full-on runtime reflection combined with
user-defined
attributes can do some powerful stuff. However, I do think that
runtime reflection
without user-defined attributes doesn't tend to be anywhere near as
useful. To
really get that sort of stuff working, we'd need D to properly
support both user-
defined attributes and runtime reflection. Both are future
possibilities but
obviously aren't happening any time soon.
- Jonathan M Davis
Ruby seems to get along without any kind of attributes/annotations.
But on the other hand you can call a method in a class declaration and
this will behave much the same as a attribute.
ActiveRecord in Rails is a good example of runtime reflection. Also
the Ruby XML library "builder" is a good example of runtime
reflection. Maybe not acutally runtime reflection but is uses the
"method_missing" method, equivalent to the "opDispatch" method in D,
heavily.
http://builder.rubyforge.org/
I'm still reading up on Ruby, but so far, there are two major difference
between serialization in Ruby and in D. First, Ruby isn't a systems
programming language with pointers/unions/etc, so serializing all
members of a class is generally okay in Ruby but isn't in D. This is the
major advantage of annotations: its a fast, simple way of declaring what
should and shouldn't be serialized. Second, Ruby's support for
serialization creates a back door around its variable protection
annotations (i.e. private,package,protected,public). Now, Ruby doesn't
actually have user defined annotations as far as I can tell, but methods
are always public and variables are always private. I don't believe that
a reflection system should bypass encapsulation. The advantage of
annotations is that they allow you to declare programmer intent and
possibly separate APIs (ala const(T)) for special purposes.
Ok, lets have a look at how a serialization annotation could look like in D:
class Foo
{
@NonSerialized int x = 3;
}
Now the same can be done in Ruby, without any special syntax, like this:
class Foo
@x = 3
non_serialized :x
end
In the Ruby example "non_serialized" would be a class/static method
which recives a symbol indicating what field to skip during
serialization. Actually since Ruby is a dynamically typed language I
don't have declare "x".
What I'm trying to say is that Ruby doesn't need a special syntax for
annotations since you can in Ruby do all (most of) the things you can do
with annotations but with class methods instead.
In general, serialization breaks encapsulation, not just in Ruby. You
can break encapsulation in D as well using .tupleof and delegates to
methods.
Ruby just has a different attitude. It allows you to
* Call private methods using "send"
* Add/remove/change methods on existing classes
* Change variables declared as const
It's no like Java which holds your hand all the time. It's the same with
D, but in a different way. In D there's instead:
* Pointers
* Unions
* malloc/free/delete
--
/Jacob Carlborg
