delphi 函数过程类型 委托...？

算是一种减少单元之间的引用的方法

类似委托

unit Unit5;

interface

uses System.Classes, System.SysUtils, Vcl.Dialogs;

type
  // 声明过程类型
  TObjFuns = procedure(const str1, str2: string) of object;

  IFormattedNumber = interface
    ['{19AE4E57-A022-45B1-AA42-43FF5142D685}']
    function FormattedString: string;
    function GetName: string;
  end;

  TFormattedInteger = class(TInterfacedObject, IFormattedNumber)
  private
    FValue: Integer;
  public
    // 声明过程变量
    FPro: TObjFuns;
    constructor Create(AValue: Integer);
    destructor Destroy; override;
    function FormattedString: string;
    function GetName: string;
    procedure DoDelegate(str1, str2: string);
  end;

  TFormattedHexInteger = class(TFormattedInteger, IFormattedNumber)
    destructor Destroy; override;
    function FormattedString: string;
    function GetName: string;
  end;

implementation

{ TFormattedInteger }

constructor TFormattedInteger.Create(AValue: Integer);
begin
  inherited Create;
  DoDelegate('TFormattedInteger', 'Destroy');
  FValue := AValue;
end;

destructor TFormattedInteger.Destroy;
begin
  DoDelegate('TFormattedInteger', 'Destroy');
  inherited Destroy;
end;

procedure TFormattedInteger.DoDelegate(str1, str2: string);
begin
  // 使用过程变量
  if Assigned(FPro) then
    FPro(str1, str2);
end;

function TFormattedInteger.FormattedString: string;
begin
  Result := 'This integer is' + IntToStr(FValue);
end;

function TFormattedInteger.GetName: string;
begin
  Result := 'TFormattedInteger.GetName';
end;

{ TFormattedHexInteger }

destructor TFormattedHexInteger.Destroy;
begin
  DoDelegate('TFormattedHexInteger', 'Destroy');
  inherited Destroy;
end;

function TFormattedHexInteger.FormattedString: string;
begin
  Result := 'The hex integer is $' + IntToHex(FValue, 4);
end;

function TFormattedHexInteger.GetName: string;
begin
  Result := 'TFormattedHexInteger.GetName';
end;

end.

unit Unit4;

interface

uses
  Winapi.Windows, Winapi.Messages, System.SysUtils, System.Variants,
  System.Classes, Vcl.Graphics,
  Vcl.Controls, Vcl.Forms, Vcl.Dialogs, Vcl.StdCtrls,
  Unit5;

type
  TForm4 = class(TForm)
    btn1: TButton;
    mmo1: TMemo;
    procedure btn1Click(Sender: TObject);
  private
    procedure PrintfStr(const str1, str2: string);
    { Private declarations }
  public
    { Public declarations }
  end;

var
  Form4: TForm4;

implementation

{$R *.dfm}

procedure TForm4.btn1Click(Sender: TObject);
var
  MyInt: TFormattedInteger;
begin
  MyInt := TFormattedInteger.Create(123);
  // 给过程变量赋值
  MyInt.FPro := PrintfStr;
  mmo1.Lines.Add(MyInt.FormattedString);
  MyInt.Free;
  mmo1.Lines.Add('End of Procedure  ' + #13);

end;

procedure TForm4.PrintfStr(const str1, str2: string);
begin
  mmo1.Lines.Add(str1 + '->' + str2);
end;

end.

 ps:最近学习接口，接口代码来自:delphi COM深入编程p22