标签：
当函数（或过程）A定义在函数（或过程）B之前，那么函数B就可以调用函数A，并且编译成功，例如下面的
procedure TForm1.btn1Click(Sender: TObject); 和 function showstr: string;
unit Test;
interface
uses
Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
Dialogs, StdCtrls;
type
TForm1 = class(TForm)
btn1: TButton;
procedure btn1Click(Sender: TObject);
private
{ Private declarations }
public
{ Public declarations }
end;
var
Form1: TForm1;
implementation
{$R *.dfm}
function showstr: string;
begin
Result:= ‘lala‘;
end;
procedure TForm1.btn1Click(Sender: TObject);
begin
ShowMessage(showstr);
end;
end.
当函数（或过程）A定义在函数（或过程）B之后，那么如果函数B调用函数A，在编译时会报错，如下面的例程
还是procedure TForm1.btn1Click(Sender: TObject); 和 function showstr: string;
unit Test;
interface
uses
Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
Dialogs, StdCtrls;
type
TForm1 = class(TForm)
btn1: TButton;
procedure btn1Click(Sender: TObject);
private
{ Private declarations }
public
{ Public declarations }
end;
var
Form1: TForm1;
implementation
{$R *.dfm}
procedure TForm1.btn1Click(Sender: TObject);
begin
ShowMessage(showstr);
end;
function showstr: string; //showstr在TForm1.btn1Click后定义，且没有在它之前进行声明
begin
Result:= ‘lala‘;
end;
end.
要想当函数（或过程）A定义在函数（或过程）B之后，并且函数B调用函数A，在编译时不报错，那就需要现在B前面声明A，然后再在B中调用A，这时候无论A在B之前定义还是在B之后定义，都能够编译成功。如下面的例程
unit Test;
interface
uses
Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
Dialogs, StdCtrls;
function showstr: string; //首先在interface里面声明
type
TForm1 = class(TForm)
btn1: TButton;
procedure btn1Click(Sender: TObject);
private
{ Private declarations }
public
{ Public declarations }
end;
var
Form1: TForm1;
implementation
{$R *.dfm}
function showstr: string;
begin
Result:= ‘lala‘;
end;
procedure TForm1.btn1Click(Sender: TObject);
begin
ShowMessage(showstr);
end;
end.
标签：
原文地址：http://www.cnblogs.com/xumenger/p/4451119.html
