新手的极菜之问题～

[nchen123]

我昨天刚开始学 delphi, 正在看 delphi.about.com 上的在线教程。
学到了静态变量，为什么这段简单的示例代码都编译不过：

procedure TForm1.Button3Click(Sender: TObject);
const clicks : Integer = 1; // 静态变量
begin
Form1.Caption := '您点击了' + IntToStr(clicks) + '次';
clicks := clicks + 1; －－－－－－－>这一行出错！
end;

出错信息是
[Error] Unit1.pas(82): Left side cannot be assigned to

我用的是 delphi 6.0 的英文版。

[guanghui]

那是常量，常量是不能用来计算的，跟VB中不同

[chinalian]

常量clicks的值不能被更改。

[nchen123]

是不是这里的教程讲错了？

Variable typed constants
Although we declare typed constants in the const section of a procedure, it is important to remember that they are not constants. At any point in your application, if you have access to the identifier for a typed constant you'll be able to modify its value.

To see typed constants at work, put a button on a blank form, and assign the following code to the OnClick event handler:

procedure TForm1.Button1Click(Sender: TObject);
const clicks : Integer = 1; //not a true constant
begin
Form1.Caption := IntToStr(clicks);
clicks := clicks + 1;
end;

Notice that every time you click on the button, forms caption increments steadily.

[zhudongpo]

up

[nchen123]

sorry, 我没往下看，现在找到原因了：

要把 Project -> Options -> Complier -> Assignable typed constants 选项打开。

[sailer_shi]

你为什么要用静态变量呀？

[jacky_shen]

procedure TForm1.Button1Click(Sender: TObject);
{$J+}
const
I: Integer = 0;
{$J-}
begin
Inc(I);
Caption := IntToStr(I)
end;

也可以通过设置编译指令J，来达到局部有效的作用。

[nchen123]

不是我想用，是我刚刚学到这里，总得知道怎么用吧，

揭帖了