Am 19.03.2012 01:41, schrieb Walter Bright:
I'm sorry, I find this *massively* confusing. What is foo? Why are you
serializing something marked "NonSerialized"? I really have no idea what is
going on with this. What is the serialize() function? How does any of this tell
you how to serialize an int? How is Base.c also a NonSerialized with c in a
superclass of it?
attributes does not containing code - there just a (at-runtime)
queryable information that can be attached to serveral things (like
classes, methods, ...) - think of it like double.epsilon - but
extendable by users - thats it, and in the c# world these
attribute-definitions tend to be something like an class (but without code)
in c# you can walk by (runtime)reflection through your code and find out
if something is annotated with an special attribute and use the
configure information and do something with it - call an constructor,
open an connection, generated code (at runtime) - whatever you want
its a easy-to-use-buildin-attribution-system thats it - and people like
them because c# do all the big magic by giving developers a bunch of
attributes that are then used for stuff like serialization,
memory-layout, ...
a compiletime example of this could be:
attribute my_special_attribute
{
int version;
}
attribute my_special_attribute2
{
string test;
}
class test
{
[my_special_attribute(version=2)]
int method1();
[my_special_attribute(version=2)]
[my_special_attribute2(test="bert")]
int method2();
}
void main()
{
auto b = [ __traits(allMembers, D) ];
foreach( auto a; b )
{
-->attribute query magic
-->auto c = [ __traits(attribute("my_special_attribute", a) ];
-->auto c = [ __traits(attribute("my_special_attribute2", a) ];
//now we know all methods with my_special_attribute
//and speical_special_attribute2 and their content (version=2
//and test="bert"
//now think of an template or mixing that uses this
//information for code-generation or something like that
//thats all
}
}
