[fpc-devel] .NET Reflection vs RTTI

[Thorsten Engler]

> I'm wondering if anybody has sufficient knowledge in this (I don't).
> Many developers that moved over to the dark side (.NET) using 
> Delphi.Net or C# always rave about .Net Reflection and how 
> much better it is to RTTI.

> Anybody actually know what is better?  What limits are they 
> talking about in RTTI?
> I have used RTTI extensively in my work and I don't seem to 
> have any issues with it, but clearly I am missing something!

RTTI in native Delphi / FPC is just the pure data structures that the
compiler generated and by and large you are on your own to decipher them
once you got a pointer to it. Reflection in .NET on the other hand is a
higher level object oriented Framework which sits on top of the actual
metadata and gives relatively easy and comfortable access to that
information. 

As far as the information itself that's available through RTTI / Reflection
is concerned, the type information available in .NET is truly complete, down
to every field and every method of every type. Also, the ability to
associate any number of custom attributes with any of the entities that make
up the type information in .NET is a very powerful tool.

Another huge advantage of Reflection in .NET over RTTI as provided by Delphi
and FPC is that given an instance of an object and a MethodInfo object
describing any of the accessible methods of that object it is trivial to
call that method using MethodInfo.Invoke(Instance, [Array, Of, Parameters]).
(Access to fields, properties and event is similar easy using the respective
*Info objects).

The combination of this (truly complete type information, easy access,
custom attributes) makes it rather trivial to e.g. tag private fields of a
class with the [Serializable] attribute and use Reflection to serialize the
class to/from a stream.

Cheers,
Thorsten