Question

我有以下组件，其中包含从自定义类派生的属性：

unit MyComponentTest3;

interface

uses  Windows, ExtCtrls,Classes,Controls;

type

  TMyClass3 = class
    myString: string;
    myNumber: double;
  end;

  TMyComponentTest3 = class(TCustomPanel)
  private
    FMyProperty: TMyClass3;

    procedure SetMyProperty(Value: TMyClass3);
  public
    constructor Create(AOwner: TComponent); override;
    destructor Destroy; override;

    procedure SetMyPropertyPublic(AmyString: string; AmyNumber: double);
  published
    property MyProperty: TMyClass3 read FMyProperty write SetMyProperty;
  end;

procedure Register;

implementation


procedure Register;
begin
  RegisterComponents('MyComponents', [TMyComponentTest3]);
end;

{ TMyComponentTest3 }

constructor TMyComponentTest3.Create(AOwner: TComponent);
begin
  inherited;

  FMyProperty:= TMyClass3.Create;

end;

destructor TMyComponentTest3.Destroy;
begin
  FMyProperty.Free;

  inherited;
end;

procedure TMyComponentTest3.SetMyProperty(Value: TMyClass3);
begin
with FMyProperty do
  begin
    myString:= Value.myString;
    myNumber:= Value.myNumber;
  end;
end;

procedure TMyComponentTest3.SetMyPropertyPublic(AmyString: string;
  AmyNumber: double);
var
  auxMyProperty: TMyClass3;
begin

  auxMyProperty:= TMyClass3.Create;

  with auxMyProperty do
  begin
    myString:= AmyString;
    myNumber:= AmyNumber;
  end;

  SetMyProperty(auxMyProperty);

  auxMyProperty.Free;

end;

end.

它工作正常，但是当我在设计时设置属性的值并运行程序时，值会消失。如果我设置组件的值，保存所有内容，当我加载值时，我得到的问题不再存在......

我想这个问题是因为我一直在创建自定义类的实例，但我不确定，而且我不知道如何解决这个问题。有谁知道我该怎么做？

Answer 1

TMyClass3需要从TPersistent派生才能在DFM中流式传输。它还应该可选地覆盖虚拟Assign()方法，SetMyProperty()然后可以调用该方法。

试试这个：

unit MyComponentTest3;

interface

uses
  Windows, ExtCtrls, Classes, Controls;

type

  TMyClass3 = class(TPersistent)
  private
    FMyString: string;
    FMyNumber: double;
  public
    procedure Assign(Source: TPersistent); override;
  published 
    property myString: string read FMyString write FMyString;
    property myNumber: double read FMyNumber write FMyNumber;
  end;

  TMyComponentTest3 = class(TCustomPanel)
  private
    FMyProperty: TMyClass3;

    procedure SetMyProperty(Value: TMyClass3);
  public
    constructor Create(AOwner: TComponent); override;
    destructor Destroy; override;

    procedure SetMyPropertyPublic(AmyString: string; AmyNumber: double);
  published
    property MyProperty: TMyClass3 read FMyProperty write SetMyProperty;
  end;

procedure Register;

implementation


procedure Register;
begin
  RegisterComponents('MyComponents', [TMyComponentTest3]);
end;

{ TMyClass3 }

procedure TMyClass3.Assign(Source: TPersistent);
begin
  if Source is TMyClass3 then
  begin
    with TMyClass3(Source) do
    begin
      Self.FMyString := myString;
      Self.FMyNumber := myNumber;
    end;
  end else
    inherited;
end;

{ TMyComponentTest3 }

constructor TMyComponentTest3.Create(AOwner: TComponent);
begin
  inherited;
  FMyProperty := TMyClass3.Create;
end;

destructor TMyComponentTest3.Destroy;
begin
  FMyProperty.Free;
  inherited;
end;

procedure TMyComponentTest3.SetMyProperty(Value: TMyClass3);
begin
  FMyProperty.Assign(Value);
end;

procedure TMyComponentTest3.SetMyPropertyPublic(AmyString: string; AmyNumber: double);
begin
  with MyProperty do
  begin
    myString := AmyString;
    myNumber := AmyNumber;
  end;  
end;

end.

Answer 2

constructor TMyComponentTest3.Create(AOwner: TComponent);
begin
  inherited;
  FMyProperty := TMyClass3.Create;
  FMyProperty.SetSubComponent(True);
end;

设计时属性的值不会在运行时出现

2 个答案: