unit DllExport;    interface    uses Windows, Classes, Forms, DllUtils, BaseFrm; type // Inherited from TInterfacedObject to be reference-counted. TPlugin = class(TInterfacedObject, IPlugin) private FForm: TBaseForm; public destructor Destroy; override; function CreateForm(hMainForm: THandle): THandle; procedure DestroyForm; function ShowModalForm: Integer; end; function CreatePlugin(hApp: THandle): IPlugin; export; stdcall; exports CreatePlugin; var g_ConcreteClass: TBaseFormClass := nil; g_PluginIntf: IPlugin = nil; g_DllAppHandle: THandle; implementation uses Dialogs, SysUtils; ...... ..... 請問有時候 Uses寫在implementation下面,請問寫在之前或之後有何不一樣?? 發表人 - ddy 於 2002/11/28 13:41:07 發表人 - ddy 於 2002/11/28 13:53:52

You cannot use the type/const defined in a unit before using it. 'Use' after implementation can work around with the circular reference problem. e.g.

unit Unit1;
interface
uses Unit2
type
    TMyClass = class
....    unit Unit2;
....
implementation
uses Unit1;
....
var
    A: TObject;
begin
....
     TMyClass(A).xxxx
....
end;

Since Unit1 has used Unit2, Unit2 cannot use Unit1 in the interface section and the work around is to use Unit1 in the implementation section. 發表人 - william 於 2002/11/20 16:37:53