System.New、System.Dispose - 为某个指针申请和释放内存

unit Unit1;

interface

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

type
TForm1 = class(TForm)
Button1: TButton;
Button2: TButton;
Button3: TButton;
procedure Button1Click(Sender: TObject);
procedure Button2Click(Sender: TObject);
procedure Button3Click(Sender: TObject);
end;

var
Form1: TForm1;
implementation

{$R *.dfm}

Type
TMyRec = record     {定义结构}
name: string[8];
age : Word;
end;
PMyRec = ^TMyRec;   {定义结构指针; Delphi 一般把它定义在结构前面, 都可以}

{如果直接使用结构, 不使用指针}
procedure TForm1.Button1Click(Sender: TObject);
var
r: TMyRec;
begin
r.name := '张三';
r.age := 99;
ShowMessage(Format('%s %d 岁', [r.name, r.age])); {张三 99 岁}
end;

{如果使用结构指针}
procedure TForm1.Button2Click(Sender: TObject);
var
pr: PMyRec;
begin
New(pr);            {分配内存}
pr^.name := '张三';
pr^.age := 99;
ShowMessage(Format('%s %d 岁', [pr^.name, pr^.age])); {张三 99 岁}
Dispose(pr);        {释放内存}
end;

{Delphi 允许使用结构时做如下简化}
procedure TForm1.Button3Click(Sender: TObject);
var
pr: PMyRec;
begin
New(pr);
pr.name := '张三';
pr.age := 99;
ShowMessage(Format('%s %d 岁', [pr.name, pr.age])); {张三 99 岁}
Dispose(pr);
end;

end.