TObjectDispatchInvoke (Delphi)

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Description

This example illustrates the usage of TObjectDispatch. A class that acts as an Automation controller is defined—TMyClass—with a method that takes no arguments and returns an integer—MyMethod. An IDispatch instance is used to invoke MyMethod. Note that the invocation is done with the help of a dispid (dispatch identifier) obtained with the GetIDsOfNames method.

Code

program TObjectDispatch;

{$APPTYPE CONSOLE}

uses
  SysUtils,
  ObjComAuto,
  ActiveX,
  Variants;

{$METHODINFO ON}

type
  TMyClass = class
  public
    function MyMethod(): Integer;
  end;

function TMyClass.MyMethod(): Integer;
begin
  Writeln('Inside MyMethod');
  Result := 10;
end;

var
  Result: HRESULT;
  MyInstance: TMyClass;
  Dispatcher: IDispatch;
  DispathIdentifier: Integer;
  MethodName: string;
  MethodResult: OleVariant;
  Param: array of OleVariant;

begin
  MyInstance := TMyClass.Create;
  Dispatcher := ObjComAuto.TObjectDispatch.Create(MyInstance, False);

  MethodName := 'MyMethod';

  Result := Dispatcher.GetIDsOfNames(GUID_NULL, @MethodName, 1,
    SysLocale.DefaultLCID, @DispathIdentifier);

  Result := Dispatcher.Invoke(DispathIdentifier, GUID_NULL,
    SysLocale.DefaultLCID, DISPATCH_METHOD, Param, @MethodResult, nil, nil);

  if Result = S_OK then
  begin
    Writeln('Invoke return value is S_OK');
    Writeln('MethodName return value is ' + IntToStr(MethodResult));
  end
  else
  begin
    Writeln('Invoke return value is ' + IntToStr(Result));
  end;

end.

Console Output

Inside MyMethod
Invoke return value is S_OK
MyMethod return value through Invoke is 10

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