for 循环的例子

unit Unit1;

interface

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

type
TForm1 = class(TForm)
Button1: TButton;
Button2: TButton;
Button3: TButton;
Button4: TButton;
procedure Button1Click(Sender: TObject);
procedure Button2Click(Sender: TObject);
procedure Button3Click(Sender: TObject);
procedure Button4Click(Sender: TObject);
procedure FormCreate(Sender: TObject);
procedure FormDestroy(Sender: TObject);
end;

var
Form1: TForm1;

implementation

{$R *.dfm}

var
List: TStringList;

procedure TForm1.FormCreate(Sender: TObject);
begin
List := TStringList.Create;
List.Add('aaa');
List.Add('bbb');
List.Add('ccc');
List.Add('ddd');
end;

// for 循环的一般用法
procedure TForm1.Button1Click(Sender: TObject);
var
i: Integer;
s: string;
begin
for i := 0 to List.Count - 1 do
begin
s := List[i];
ShowMessage(s);
end;
end;

//还有这样用的
procedure TForm1.Button2Click(Sender: TObject);
var
i: Integer;
s: string;
begin
for i := 0 to Pred(List.Count) do
begin
s := List[i];
ShowMessage(s);
end;
end;

//还是 for in 最方便
procedure TForm1.Button3Click(Sender: TObject);
var
s: string;
begin
for s in List do
begin
ShowMessage(s);
end;
end;

//反向
procedure TForm1.Button4Click(Sender: TObject);
var
i: Integer;
s: string;
begin
for i := List.Count - 1 downto 0 do
begin
s := List[i];
ShowMessage(s);
end;
end;

procedure TForm1.FormDestroy(Sender: TObject);
begin
List.Free;
end;

end.