Delphi中as和is是用来干什么的?请给下具体的解释和例子.我是个初学者,
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![Delphi中as和is是用来干什么的?请给下具体的解释和例子.我是个初学者,](/uploads/image/z/13429365-69-5.jpg?t=Delphi%E4%B8%ADas%E5%92%8Cis%E6%98%AF%E7%94%A8%E6%9D%A5%E5%B9%B2%E4%BB%80%E4%B9%88%E7%9A%84%3F%E8%AF%B7%E7%BB%99%E4%B8%8B%E5%85%B7%E4%BD%93%E7%9A%84%E8%A7%A3%E9%87%8A%E5%92%8C%E4%BE%8B%E5%AD%90.%E6%88%91%E6%98%AF%E4%B8%AA%E5%88%9D%E5%AD%A6%E8%80%85%2C)
Delphi中as和is是用来干什么的?请给下具体的解释和例子.我是个初学者,
Delphi中as和is是用来干什么的?
请给下具体的解释和例子.
我是个初学者,
Delphi中as和is是用来干什么的?请给下具体的解释和例子.我是个初学者,
as是把某个类型对象转换成所需要的类型.
is是判断某对象是否是某类型.
例如:
unit Unit1;
interface
uses
Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
Dialogs, StdCtrls;
type
TForm1 = class(TForm)
Edit1: TEdit;
Edit2: TEdit;
Edit3: TEdit;
Button1: TButton;
procedure Button1Click(Sender: TObject);
private
{ Private declarations }
public
{ Public declarations }
end;
var
Form1: TForm1;
implementation
{$R *.dfm}
procedure TForm1.Button1Click(Sender: TObject);
var i:Integer;
begin
for i:= 0 to ControlCount - 1 do
begin
if Controls[i] is TEdit then //判断对象Controls[i]是否为TEdit类型
if (Controls[i] as TEdit).Text '' then //将对象Controls[i]转换成TEdit类型
begin
(Controls[i] as TEdit).Text := 'haha';//将对象Controls[i]转换成TEdit类型
end;
end;
end;
end.
窗体控件
Tedit 1、Tedit 2、Tedit 3、Tbutton