1

Destroy()我在这种从未被调用的情况下运行。

unit Unit2;

interface

type

// Interface
ITest = Interface(IInterface)
 function IsTrue() : Boolean;
end;

TmyClass = class(TInterfacedObject, ITest)
  public
    // Interface implementation
    function IsTrue() : Boolean;

    constructor Create();
    destructor Destroy(); override;
end;

implementation

constructor TmyClass.Create();
begin
  inherited Create();
end;

destructor TmyClass.Destroy();
begin
  inherited Destroy();
end;

published
  // Property
  property IsItTrue: Boolean read IsTrue;
end.

unit Unit1;

interface

uses
  Winapi.Windows, Winapi.Messages, System.SysUtils, System.Variants, 
  System.Classes, Vcl.Graphics, Vcl.Controls, Vcl.Forms, 
  Vcl.Dialogs, Vcl.StdCtrls, unit2;

type
  TForm1 = class(TForm)
  Button1: TButton;
  procedure FormCreate(Sender: TObject);
  procedure Button1Click(Sender: TObject);
private
  { Private declarations }
public
  { Public declarations }
end;

var
  Form1: TForm1;
  fMyClass: TmyClass;

implementation

{$R *.dfm}

procedure TForm1.Button1Click(Sender: TObject);
begin
  fMyClass.Free;  // if refcount = 0 this works, if refcount <> 0 pointer error.
  //or
  fMyClass := Nil; // no error but Destroy wil not be executed
  Close();
end;

procedure TForm1.FormCreate(Sender: TObject);
begin
  fMyClass := TMyClass.Create();
end;
end.

阅读这篇文章,只有一个构造函数,没有实现析构函数。

这有什么特别的原因吗?

我是否应该释放(如果需要)将myClass通过实现一个finalization部分来定义的所有其他对象?

4

2 回答 2

6

未调用析构函数的最可能原因是您没有将对象分配给接口变量。

procedure Test1;
var
  vMyObj : TObject;
begin
  vMyObj := myclass.Create;
end; <-Destructor NOT called here

procedure Test2;
var
  vMyIntf : IInterface;
begin
  vMyIntf := myclass.Create;
end; <-Destructor IS called here.

如果是这种情况,我邀请您阅读此答案以获取更多信息。

于 2019-12-02T15:15:55.763 回答
1

您的fMyClass变量是对象引用,而不是接口,因此它不参与TInterfaceObject的引用计数。

你需要改变这个:

fMyClass: TmyClass;

对此:

fMyClass: ITest;

然后你可以完全摆脱fMyClass.Free;

unit Unit1;

interface

uses
  Winapi.Windows, Winapi.Messages, System.SysUtils, System.Variants, 
  System.Classes, Vcl.Graphics, Vcl.Controls, Vcl.Forms, 
  Vcl.Dialogs, Vcl.StdCtrls, unit2;

type
  TForm1 = class(TForm)
  Button1: TButton;
  procedure FormCreate(Sender: TObject);
  procedure Button1Click(Sender: TObject);
private
  { Private declarations }
public
  { Public declarations }
end;

var
  Form1: TForm1;
  fMyClass: ITest;

implementation

{$R *.dfm}

procedure TForm1.Button1Click(Sender: TObject);
begin
  fMyClass := nil; // no error and Destroy will be executed
  Close();
end;

procedure TForm1.FormCreate(Sender: TObject);
begin
  fMyClass := TMyClass.Create();
end;

end.

fMyClass := nil;fMyClass仅当是接口变量而不是对象引用并且您不能调用接口变量时才会调用引用计数Free()

于 2019-12-02T22:09:09.440 回答