关于 TStringList.Assign - 回复 "u9cm" 的问题

问题来源: http://www.cnblogs.com/del/archive/2008/12/29/1230404.html#1416838

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譬如有两个 TStringList 对象: List1 和 List2;

List2.Assign(List1) 就是把 List1 的内容复制给 List2;

List2 := List1 相当于给 List1 再取一个名字.

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举例:

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unit Unit1;



interface



uses

  Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,

  Dialogs, StdCtrls;



type

  TForm1 = class(TForm)

    Button1: TButton;

    Button2: TButton;

    procedure Button1Click(Sender: TObject);

    procedure Button2Click(Sender: TObject);

  end;



var

  Form1: TForm1;



implementation



{$R *.dfm}



procedure TForm1.Button1Click(Sender: TObject);

var

  List1,List2: TStringList;

begin

  List1 := TStringList.Create;

  List2 := TStringList.Create;



  List1.CommaText := 'AAA,BBB,CCC';



  List2.Assign(List1); {此时 List1、List2 分别指向了不同的对象}

  ShowMessageFmt('%s, %p', [List1[0], Pointer(List1)]); { AAA, 00ABAA40 }

  ShowMessageFmt('%s, %p', [List2[0], Pointer(List2)]); { AAA, 00ABAA90 }



  List1.Free;

  ShowMessage(List2[1]); {List1 释放后, List2 还会存在.}

  List2.Free;

end;



procedure TForm1.Button2Click(Sender: TObject);

var

  List1,List2: TStringList;

begin

  List1 := TStringList.Create;

  List1.CommaText := 'AAA,BBB,CCC';



  List2 := List1;          {此时 List1、List2 指向了同一个对象}

  ShowMessageFmt('%s, %p', [List1[0], Pointer(List1)]); { AAA, 00ABAA40 }

  ShowMessageFmt('%s, %p', [List2[0], Pointer(List2)]); { AAA, 00ABAA40 }



  List1.Free;              {此时 List1、List2 指向的对象释放了}

  //ShowMessage(List2[1]); {所以这句会出错}

end;



end.