System.New、System.Dispose – 為某個指標申請和釋放記憶體

舉例:

unit Unit1;interfaceuses  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     {定義結構}    name: string[8];    age : Word;  end;  PMyRec = ^TMyRec;   {定義結構指標; Delphi 一般把它定義在結構前面, 都可以}{如果直接使用結構, 不使用指標}procedure TForm1.Button1Click(Sender: TObject);var  r: TMyRec;begin  r.name := '張三';  r.age := 99;  ShowMessage(Format('%s %d 歲', [r.name, r.age])); {張三 99 歲}end;{如果使用結構指標}procedure TForm1.Button2Click(Sender: TObject);var  pr: PMyRec;begin  New(pr);            {分配記憶體}  pr^.name := '張三';  pr^.age := 99;  ShowMessage(Format('%s %d 歲', [pr^.name, pr^.age])); {張三 99 歲}  Dispose(pr);        {釋放記憶體}end;{Delphi 允許使用結構時做如下簡化}procedure TForm1.Button3Click(Sender: TObject);var  pr: PMyRec;begin  New(pr);  pr.name := '張三';  pr.age := 99;  ShowMessage(Format('%s %d 歲', [pr.name, pr.age])); {張三 99 歲}  Dispose(pr);end;end.

System 單元下的公用函數目錄