Delphi判斷某個類是否實現了某個接口

通過TObject.GetInterface可以獲得對象的實例實現某個接口，前提條件是必須實例化對象后才能運行GetInterface

下面的方法可獲取類是否實現了某個接口，並返回接口的偏移：

function FindInterface(AClass: TClass; GUID:TGUID; var Offset:NativeInt):Boolean;
var
  i : integer;
  InterfaceTable: PInterfaceTable;
  InterfaceEntry: PInterfaceEntry;
begin
  while Assigned(AClass) do
  begin
    InterfaceTable := AClass.GetInterfaceTable;
    if Assigned(InterfaceTable) then
    begin
      for i := 0 to InterfaceTable.EntryCount-1 do
      begin
        InterfaceEntry := @InterfaceTable.Entries[i];
        if InterfaceEntry.IID=GUID then
        begin
          Offset:=InterfaceEntry.IOffset;
          Exit(True);
        end;
      end;
    end;
    AClass := AClass.ClassParent;
  end;
end;

　下面我們看下通過偏移量的快速獲得對象的接口，以及通過接口快速獲取對象：

快速獲取對象的接口：

type
  TSomeObject=class(TXXX, ISomeInterface)
  ......
  end;

var
  FItemObjectOffset:NativeInt;

//獲取偏移量
FindInterface(TSomeObject, ISomeInterface, FItemObjectOffset)

var
  P:TSomeObject;
  Intf:ISomeInterface;
....................................

//通過對象直接獲取接口
    PNativeInt(@Intf)^:=PNativeInt(@P)^+ FItemObjectOffset;
    Intf._AddRef;

　　

快速通過接口獲取對象

type
  TSomeObject=class(TXXX, ISomeInterface)
  ......
  end;

var
  FItemObjectOffset:NativeInt;

//獲取偏移量
FindInterface(TSomeObject, ISomeInterface, FItemObjectOffset)

var
  P:TSomeObject;
  Intf:ISomeInterface;
....................................

//通過接口獲取對象
  P:=TSomeObject(Pointer(PNativeInt(@Intf)^- FItemObjectOffset));