匿名方法作为函数结果 [英] Anonymous method as function result

问题描述

我想要做的是将一个匿名方法（作为函数结果我将它分配给相同类型的变量）。 Delphi抱怨无法完成分配任务。显然，Delphi的东西我想分配 GetListener函数而不是该函数的结果。非常感谢对此的任何帮助。

What I want to do is to assign an anonymous method which I get as a function result to a variable of the same type. Delphi complains about not beeing able to do the assignement. Obviously Delphi things I want to assign the "GetListener" function instead of the result of that same function. Any help with this is very much appreciated.

type
      TPropertyChangedListener = reference to procedure (Sender: TStimulus);

      TMyClass = class
        function GetListener:TPropertyChangedListener
      end;


    ....

    var MyClass: TMyClass;
        Listener: TPropertyChangedListener;
    begin
      MyClass:= TMyClass.create;
      Listener:= MyClass.GetListener;   //  Delphi compile error: E2010 Incompatible types:  TPropertyChangedListener' and 'Procedure of object' 

    end; 

推荐答案

使用以下语法：

  Listener:= MyClass.GetListener();

---

我已经写了以下示例来说明MyClass.GetListener（）和MyClass.GetListener分配之间的区别：

---

I have written the following example to make clear the difference between the MyClass.GetListener() and MyClass.GetListener assignments:

type
  TProcRef = reference to procedure(Sender: TObject);
  TFunc = function: TProcRef of object;

  TMyClass = class
    function GetListener: TProcRef;
  end;

function TMyClass.GetListener: TProcRef;
begin
  Result:= procedure(Sender: TObject)
  begin
    Sender.Free;
  end;
end;

procedure TForm1.Button1Click(Sender: TObject);
var
  MyClass: TMyClass;
  ProcRef: TProcRef;
  Func: TFunc;

begin
  MyClass:= TMyClass.Create;
// standard syntax
  ProcRef:= MyClass.GetListener();

// also possible syntax
//  Func:= MyClass.GetListener;
//  ProcRef:= Func();

  ProcRef(MyClass);
end;

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