generic Class for any Type ?

[paule32]

I have a generic Class:

Code: Pascal  [Select][+][-]

1. type
2.   generic TStream<T1> = class(TObject)

I would have a function that use a Pointer or similar to this Class:

Code: Pascal  [Select][+][-]

1. function  TStream_WriteBuffer(p: specialize TStream<T>; const Buffer; Count: Integer): Integer; stdcall; external RTLDLL;

But I fail with Error:
Error: Identifier not found "T"

[gidesa]

Code: Pascal  [Select][+][-]

1. function  TStream_WriteBuffer(p: specialize TStream<T>; const Buffer; Count: Integer): Integer; stdcall; external RTLDLL;

But I fail with Error:
Error: Identifier not found "T"

When you use the generic class, you have to instantiate the generic type parameter, that is T, with a concrete type.
For example with integer:

Code: Pascal  [Select][+][-]

1. function  TStream_WriteBuffer(p: specialize TStream<Integer>; const Buffer; Count: Integer): Integer; stdcall; external RTLDLL;

[Fibonacci]

Code: Pascal  [Select][+][-]

1. generic function TStream_WriteBuffer<T>(p: specialize TStream<T>; const Buffer; Count: Integer): Integer; stdcall; external RTLDLL;

[Khrys]

The compiler is right; there is no  "T"  in  TStream_WriteBuffer  because that function isn't generic. And you can't just change it to...

Code: Pascal  [Select][+][-]

1. generic function TStream_WriteBuffer<T>(p: specialize TStream<T>; const Buffer; Count: Integer): Integer; stdcall; external RTLDLL;

...either, because DLLs don't contain generic templates, they contain machine code. Generics are a compile-time feature, so to provide a generic function in a DLL you'd have to specialize it for every type that could ever possibly be constructed in advance - which is impossible.

If you want to distribute generic functions, you must provide source code, period.

[PascalDragon]

If you want to distribute generic functions, you must provide source code, period.

Not quite. You can't put them in a DLL, but you can distribute them as binary by simply providing the PPU file of the unit which will be enough for the compiler (assuming the unit is from the same compiler version and for the same target with compatible settings).

Similarily dynamic packages will allow the same in the future, but for PPLs (which are libraries extended with special compiler magic functionality), but even there the compiler internally relies on the PPU files embedded in the corresponding PCP file at compiletime.