Question

我正在阅读Hodges的书“Delphi中的更多编码”，关于工厂模式的部分。试着学习东西。把我的代码分解成小单元。我使用ReportMemoryLeaksOnShutDown := True;并且停止代码会导致内存泄漏。为什么会发生这种情况？如何解决？

unit Unit2;

interface

uses
  Generics.Collections, System.SysUtils;

type
  TGatewayTpe = (gtSwedbank, gtDNB);

type
  TBaseGateway = class

  end;

type
  TSwedbankGateway = class(TBaseGateway)
  end;

type
  TGatewayFunction = reference to function: TBaseGateway;

type
  TGatewayTypeAndFunction = record
    GatewayType: TGatewayTpe;
    GatewayFunction: TGatewayFunction;
  end;

type
  TGatewayFactory = class
  strict private
    class var FGatewayTypeAndFunctionList: TList<TGatewayTypeAndFunction>;
  public
    class constructor Create;
    class destructor Destroy;
    class procedure AddGateway(const AGatewayType: TGatewayTpe;
      const AGatewayFunction: TGatewayFunction);
  end;

implementation

class procedure TGatewayFactory.AddGateway(const AGatewayType: TGatewayTpe;
  const AGatewayFunction: TGatewayFunction);

var
  _GatewayTypeAndFunction: TGatewayTypeAndFunction;
begin
  _GatewayTypeAndFunction.GatewayType := AGatewayType;
  _GatewayTypeAndFunction.GatewayFunction := AGatewayFunction;

  FGatewayTypeAndFunctionList.Add(_GatewayTypeAndFunction);
end;

class constructor TGatewayFactory.Create;
begin
  FGatewayTypeAndFunctionList := TList<TGatewayTypeAndFunction>.Create;
end;

class destructor TGatewayFactory.Destroy;
begin
  FreeAndNil(FGatewayTypeAndFunctionList);
end;

initialization
  TGatewayFactory.AddGateway(
    gtSwedbank, 
    function: TBaseGateway
    begin
      Result := TSwedbankGateway.Create;
    end
  );

end.

Answer 1

这是一个编译器缺陷。在单元的初始化部分中定义匿名方法似乎导致匿名方法未被最终确定，因此泄露。在这种情况下，我会通过将代码从初始化部分移动到class constructor来解决此问题。

因此，完全删除initialization部分，并将类构造函数更改为：

class constructor TGatewayFactory.Create;
begin
  FGatewayTypeAndFunctionList := TList<TGatewayTypeAndFunction>.Create;
  AddGateway(
    gtSwedbank,
      function: TBaseGateway
      begin
        Result := TSwedbankGateway.Create;
      end
  );
end;

这是我可以编写的最简单的复制品：

unit Unit1;

interface

implementation

type
  TProc = reference to procedure;

var
  Foo: TProc;

initialization
  ReportMemoryLeaksOnShutdown := True;
  Foo := procedure begin end;

end.

如果在项目中包含此单元，则会报告匿名方法泄露。

但是这个变种没有报告泄漏：

unit Unit1;

interface

implementation

type
  TProc = reference to procedure;

var
  Foo: TProc;

procedure DoInit;
begin
  Foo := procedure begin end;
end;

initialization
  ReportMemoryLeaksOnShutdown := True;
  DoInit;

end.

缺陷在XE8中得到修复。

工厂模式，内存泄漏

1 个答案: