On 11/13/13 10:41 AM, Dmitry Olshansky wrote:
13-Nov-2013 13:27, Andrei Alexandrescu пишет:
On 11/13/13 12:55 AM, Jacob Carlborg wrote:
On 2013-11-13 05:07, Andrei Alexandrescu wrote:
Then how do you figure doing this:
class Streamable { ... }
class Foo : Streamable { ... }
class Bar : Streamable { ... }
string className = stream.readln();
Streamable obj = ...;
How do you create obj from className, when className could be either
"Foo" or "Bar"? In the general case there could be any number of
classes, in different modules.
This requires Object.factory (or equivalent) and that all subclasses
have been registered as well.
With Object.factory that's taken care of already.
I have to chime in.
Serialization != calling default constructor by name.
Of course not. It does give you access to an object with the correct
dynamic type, and interfaces and virtual calls take care of the rest.
You have to work out fields somehow - Object.factory doesn't help with
that. What serialization needs is some hook - be it delegete or whatnot:
Object deserialize(SomeStreamingAbstraction here);
Or a method.
Simply snatching a name is not serialization. Not to mention that far
too many protocols are not text.
Method.
Keeping built-in map of class-name --> "create via default constructor"
is an awful example of ONE SIZE FITS ALL. It doesn't!
It is: it achieves virtual construction, the only missing piece in a
classic OOP scheme. Once you have the object, the rest is smooth sailing.
Simply on the ground of "solves problem in too narrow scope for a hefty
coast to the user" I'd drop it.
It's good. Let's keep it.
Andrei
