自定义类问题
新开一个delphi应用程序，在默认的type
TForm1 = class(TForm)代码处加入自己写的类，为啥报：Unsatisfied forward or external declaration错误？

加入的代码如下(叫TMyClass):
uses
Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
Dialogs;

type
TMyClass = class(TObject) //加入自定义类TMyClass,只声明一个方—oSomeThing
procedure DoSomeThing;
end;

TForm1 = class(TForm)
private
{ Private declarations }
public
{ Public declarations }
end;

var
Form1: TForm1;

implementation

{$R *.dfm}

end.
[解决办法]
要在implementation处实现：
procedure TMyClass.DoSomething;
begin
////
end;