过程类型,方法类型

下面是对两种数据类型的认识(过程类型,方法类型)

1.过程类型

unit Unit1;interfaceuses Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms, Dialogs, StdCtrls;type TForm1 = class(TForm) Button1: TButton; procedure Button1Click(Sender: TObject); private { Private declarations } public { Public declarations } end;var Form1: TForm1;implementation{$R *.dfm}type TOneFun=function(X:Integer):Integer;function SomeFunction(X:Integer):Integer;begin Result:=X*2end;function SomeCallBack(X:Integer;OneFun:TOneFun):Integer; //这个相当于一个回调函数begin Result:=OneFun(X);end;procedure TForm1.Button1Click(Sender: TObject);var F:TOneFun; I,J:Integer;begin F:=SomeFunction; I:=F(4); j:=SomeCallBack(4,F); if i=j then showmessage('F(4)和SomeCallBack功能相同'); showmessage(inttostr(i)); showmessage(inttostr(j));end;end.

 

2.方法类型

unit Unit1;interfaceuses Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms, Dialogs, StdCtrls;type TForm1 = class(TForm) Button1: TButton; procedure Button1Click(Sender: TObject); private { Private declarations } public { Public declarations } procedure ShowInfo; end;var Form1: TForm1;implementation{$R *.dfm}{ 方法指针可以用定义在System单元的一个记录描述 type TMethod=record code,data :Pointer; 它包含两个指针code和data,code可以看作是方法地址的指针,data可以看做是方法所属对 象的指针}procedure TForm1.Button1Click(Sender: TObject);type TMyProcedure=procedure of object; //定义了一个方法类型var OneProcedure:TMyProcedure; //声明一个方法类型的变量begin OneProcedure:=Form1.ShowInfo; //给方法指针赋值 { 也可以这样给方法指针赋值 TMethod(OneProcedure).code:=Form1.MethodAddress('showinfo'); TMethod(OneProcedure).data:=Form1; } ShowMessage(TObject(TMethod(OneProcedure).Data).ClassName); OneProcedure;end;procedure TForm1.ShowInfo;begin ShowMessage(Self.Name);end;end.

过程类型的变量是指向过程的指针，和回调函数差不多，方法类型的变量是指向方法的指针，写法上还比过程类型多了 of objects,方法类型的变量只能通过对象来引用