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System.SysUtils.Supports

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Delphi

function Supports(const Instance: IInterface; const IID: TGUID; out Intf): Boolean;
function Supports(const Instance: TObject; const IID: TGUID; out Intf): Boolean;
function Supports(const Instance: IInterface; const IID: TGUID): Boolean;
function Supports(const Instance: TObject; const IID: TGUID): Boolean;
function Supports(const AClass: TClass; const IID: TGUID): Boolean;

C++

extern DELPHI_PACKAGE bool __fastcall Supports(const System::_di_IInterface Instance, const GUID &IID, /* out */ void *Intf)/* overload */;

Contents

Properties

Type Visibility Source Unit Parent
function public
System.SysUtils.pas
System.SysUtils.hpp
System.SysUtils System.SysUtils

Description

Indicates whether a given object or interface supports a specified interface.

Call Supports to determine whether the object or interface specified by Instance, or the class specified by AClass, supports the interface identified by the IID parameter. If Instance supports the interface, Supports returns the interface as the Intf parameter and returns True. If AClass supports the interface, Supports does not return an interface, but still returns True. If the interface specified by IID is not supported, Supports returns False.

On the Win32 platform, to determine whether the interface specified by IID is supported, Supports calls the QueryInterface method of the supplied interface (or the interface of the supplied object). However, unlike calling QueryInterface directly, Supports lets you pass a nil (Delphi) or NULL (C++) value as the instance.

On the .NET platform, Supports uses the typecasting facilities of the .NET framework.

Warning

With the exception of the overload that checks whether a TClass implements an interface, all the other versions of Supports will extract an interface reference either from an object or from another interface reference, causing the reference count of the underlying object to be incremented, and then will release the interface upon exit (decrementing the reference count). For objects that have a reference count of zero, this will result in the object destruction.

var 
  Obj: TInterfacedObject;
begin
  Obj := TInterfacedObject.Create;
  if Supports(Obj, IInterface) then { ... at this point Obj will be freed }
end;

See Also

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