在Delphi中，我可以使用一個被破壞的對象而不會出錯！可能嗎？

Question

我正在嘗試使用線程進行Web服務調用。出於這個原因，我定義了一個簡單的對象並從一個線程調用它的方法。

但我意識到，銷燬該對象後，我仍然可以使用它的方法沒有任何錯誤，它會返回正確的答案。怎麼可能？你有什麼評論嗎？

// TThreadMethod is defined in Classes.pas 

TThreadMethod = procedure of object; 


********************* 
     Interface 
********************* 

TMyObject = class(TObject) 
    procedure DoSomething; 
end; 

TMyThread = class(TThread) 
private 
    FMethod : TThreadMethod; 
protected 
    procedure Execute; override; 
public 
    constructor Create(aMethod: TThreadMethod); 
end; 

********************* 
    Implementation 
********************* 

// I called the thread and destroyed the object immediately. 

procedure TForm1.Button1Click(Sender: TObject); 
var 
    aObject : TMyObject; 
begin 
    aObject := TMyObject.Create; 
    TMyThread.Create(aObject.DoSomething); 
    FreeAndNil(aObject); // Object itself was destroyed here. 
end; 

constructor TMyThread.Create(aMethod: TThreadMethod); 
begin 
    inherited Create(True); 
    FreeOnTerminate := True; 
    FMethod := aMethod; 
    Resume; 
end; 

procedure TMyThread.Execute; 
begin 
    Sleep(10000); // wait 10 sec. before calling the method 
    // The object was already destroyed but it doesn't produce any error! 
    FMethod; // It calls the web service method and returns correct result. But how???  
end; 

procedure TMyObject.DoSomething; 
begin 
    // Call a web service method and show the result on the form. 
end; 

Answer 1

的方法是不依賴於對象，但對類...

type 
TMyObject = class(TObject) 
published 
    procedure DoSomething; 
end; 
TSomeProcedure=Procedure of object; 

    TForm1 = class(TForm) 
    ..... 
    end; 

var 
    Form1: TForm1; 

implementation  
{$R *.dfm}  
procedure TForm1.Button2Click(Sender: TObject); 
var 
p:TSomeProcedure; 
M:TMethod; 
begin 
m.Code := TMyObject.MethodAddress('DoSomething'); 
m.Data := nil; 
p := TSomeProcedure(m); 
p; 
end; 

procedure TMyObject.DoSomething; 
begin 
    Showmessage('Hallo'); 
end; 

EDIT一個附加的例子將是

type 
TMyObject = class(TObject) 
published 
    procedure DoSomething; 
end; 
procedure TMyObject.DoSomething; 
begin 
    Showmessage('Hallo'); 
end; 

procedure TForm1.Button1Click(Sender: TObject); 
var 
o1,o2:TMyObject; 
begin 
o1:=TMyObject.Create; 
o2:=TMyObject.Create; 
Memo1.Lines.Add(IntToHex(Integer(TMyObject.MethodAddress('DoSomething')),4)); 
Memo1.Lines.Add(IntToHex(Integer(o1.MethodAddress('DoSomething')),4)); 
Memo1.Lines.Add(IntToHex(Integer(o2.MethodAddress('DoSomething')),4)); 
o1.Free; 
o2.Free; 
end;