在表单中创建 Delphi 对象

Question

我有一个 Delphi 表单，其中没有任何组件。然后，我创建了一个包含多个 classes 的单元。我一直在尝试实例化 class 并在表单中创建一个对象，但它抱怨 class 未声明。这是错误消息：'E2003 Undeclared Identifier:TUser'。

这是项目：

程序测试；

uses
  Forms,
  Home in 'Home.pas' {Form1},
  uUser in 'uUser.pas';

{$R *.res}

begin
  ReportMemoryLeaksOnShutdown := DebugHook <> 0;
  Application.Initialize;
  Application.Run;
end.

这是我的空表格：

unit Home;

interface

uses
  Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
  Dialogs, uUser;

type
  TForm1 = class(TForm)
  private
    { Private declarations }
protected

  public
    { Public declarations }
   u : TUser; //It's complaining about TUser. I can right click on 
   TUser, and it will take me to the class declaration. 

  end;
var
  Form1: TForm1;

implementation
{$R *.dfm}

end.

这是我创建的 Class：

unit uUser;

interface

uses
  classes,SysUtils,Dialogs;

implementation

type
TAddress = class
private
 FStreetAddress : string;
 FCity          : string ;
 FState         : string;
 FZipCode       : string;

 procedure setStreetAddress(const Value : string);
 procedure setCity(const Value : string);
 procedure setState(const Value : string);
 procedure setZipCode(const Value : string);

 protected

 public
 property StreetAddress : string read FStreetAddress write setStreetAddress;
 property City : string read FCity write setCity;
 property State : string read FState write setState;
 property ZipCode : string read FZipCode write setZipCode;


end;

type
  TPermanentAdddress = class (TAddress)
  private
  FStartDate     : string;
  FEndDate       : string;

  procedure setStartDate(const Value : string);
  procedure setEndDate(const Value : string);

  protected

  public

  property StartDate : string read FStartDate write setStartDate;
  property EndDate   : string read FEndDate write setEndDate ;
  end;


type
TUser = class(TComponent)
  private
  FFirstName : string;
  FAddress : TPermanentAdddress;
  procedure setFirstName(const Value : string);
  procedure setAddress(const Value : TPermanentAdddress);

  protected

  public
  constructor Create(); reintroduce; overload;
  destructor Destroy();  override;
   property FirstName : string read FFirstName write setFirstName;
   property Address : TPermanentAdddress read FAddress write setAddress;

end;

procedure TAddress.setStreetAddress(const Value : string);
begin
  FStreetAddress := value;
end;

 procedure TAddress.setCity(const Value : string);
 begin
   FCity := Value;
 end;
 procedure TAddress.setState(const Value : string);
 begin
   FState := Value;
 end;
 procedure TAddress.setZipCode(const Value : string);
 begin
   FZipCode := Value;
 end;

 //Permanent Address
  procedure TPermanentAdddress.setStartDate(const Value : string);
  begin
    FStartDate := value;
  end;
  procedure TPermanentAdddress.setEndDate(const Value : string);
  begin
    FEndDate := Value;
  end;

  //tvxpatient
  procedure TUser.setFirstName(const Value : string);
  begin
    FFirstName := Value;
  end;
  procedure TUser.setAddress(const Value : TPermanentAdddress);
  begin
    FAddress := Value;
  end;

  constructor TUser.Create();
  begin
   FAddress := TPermanentAdddress.Create;
  end;

  destructor TUser.Destroy();
  begin
  //FAddress.Free;
  end;

end.

Answer 1

您所有的 classes 都在 implementation 部分，这意味着它们在单元本身之外是不可见的。将它们移至 interface 部分。

unit uUser;

interface

uses
  classes,SysUtils,Dialogs;

interface

type
  TAddress = class
  private
    FStreetAddress : string;
    FCity          : string ;
    FState         : string;
    FZipCode       : string;

    procedure setStreetAddress(const Value : string);
    procedure setCity(const Value : string);
    procedure setState(const Value : string);
    procedure setZipCode(const Value : string);
  protected
  public
    property StreetAddress : string read FStreetAddress write setStreetAddress;
    property City : string read FCity write setCity;
    property State : string read FState write setState;
    property ZipCode : string read FZipCode write setZipCode;
  end;

type
  TPermanentAdddress = class (TAddress)
  private
    FStartDate     : string;
    FEndDate       : string;
    procedure setStartDate(const Value : string);
    procedure setEndDate(const Value : string);
  protected
  public
    property StartDate : string read FStartDate write setStartDate;
    property EndDate   : string read FEndDate write setEndDate ;
  end;

type
  TUser = class(TComponent)
  private
    FFirstName : string;
    FAddress : TPermanentAdddress;
    procedure setFirstName(const Value : string);
    procedure setAddress(const Value : TPermanentAdddress);
  protected
  public
    constructor Create(); reintroduce; overload;
    destructor Destroy();  override;
    property FirstName : string read FFirstName write setFirstName;
    property Address : TPermanentAdddress read FAddress write setAddress;
end;

implementation

procedure TAddress.setStreetAddress(const Value : string);
begin
  FStreetAddress := value;
end;

 procedure TAddress.setCity(const Value : string);
 begin
   FCity := Value;
 end;
 procedure TAddress.setState(const Value : string);
 begin
   FState := Value;
 end;
 procedure TAddress.setZipCode(const Value : string);
 begin
   FZipCode := Value;
 end;

 //Permanent Address
  procedure TPermanentAdddress.setStartDate(const Value : string);
  begin
    FStartDate := value;
  end;
  procedure TPermanentAdddress.setEndDate(const Value : string);
  begin
    FEndDate := Value;
  end;

  //tvxpatient
  procedure TUser.setFirstName(const Value : string);
  begin
    FFirstName := Value;
  end;
  procedure TUser.setAddress(const Value : TPermanentAdddress);
  begin
    FAddress := Value;
  end;

  constructor TUser.Create();
  begin
   FAddress := TPermanentAdddress.Create;
  end;

  destructor TUser.Destroy();
  begin
  //FAddress.Free;
  end;

end.

此外，请注意：从 TComponent 下降的唯一原因是创建将出现在组件面板上的组件（这意味着它们需要一个 Register 过程）。如果您不设计将在设计时放置在表单上的组件，则它们不需要 TComponent 作为祖先的开销 - 它们可以简单地从 TObject 继承，这将您的 TUser class.

似乎就是这种情况

在表单中创建 Delphi 对象

Creating a Delphi Object in a Form

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