delphi - 类之间的循环引用

Question

我需要开发下一个图表类:
我编写了代码，但是存在循环单元引用的问题。

XmlFileManager 类包含:

unit XmlFileManager;
interface
uses
  xmldom, XMLIntf, msxmldom, XMLDoc, SysUtils, DateUtils, Classes, Dialogs,
  XmlEnpManager;
type
  TXmlFileManager = class
  private
    [...]
    xmEnp: TXmlEnpManager;
    xmEnpInicial: TXmlEnpManager;
    xmEnpFinal: TXmlEnpManager;
[...]
end.

抽象类，XmlNodeManager:

unit XmlNodeManager;
interface
uses
  xmldom, XMLIntf, msxmldom, XMLDoc, SysUtils, DateUtils, Classes, Dialogs,
  XmlFileManager;
type
  TXmlNodeManager = class
   protected
        { sgy alias para strategy }
        sgyIterator: Integer;
        sgyContext: TXmlFileManager;
        sgyAttributes: TStringList;
        sgyNode: IXMLNode;
[...]
end.

以及 XmlEnpManager 具体类:

unit XmlEnpManager;
interface
uses
  xmldom, XMLIntf, msxmldom, XMLDoc, SysUtils, DateUtils, Classes, Dialogs,
  XmlNodeManager;
type
  TXmlEnpManager = class (TXmlNodeManager)
    public
        constructor Create(aContext: TXmlFileManager); overload; override;
        constructor CreateInicial(aContext: TXmlFileManager); reintroduce; overload;
        constructor CreateFinal(aContext: TXmlFileManager); reintroduce; overload;
[...]
end.

构建失败并出现错误:

[dcc32 Fatal Error] XmlNodeManager.pas(7): F2047 Circular unit reference to 'XmlFileManager'

有什么想法可以解决这个问题吗？

Answer 1

将 TXmlFileManager 和 TXmlNodeManager 放在相同的 unit 和相同的 type 部分中，然后确保type 部分从此类开始:TXmlNodeManager = class;

参见官方文档:Forward Declarations and Mutually Dependent Classes .

unit XmlFileManagerAndXmlNodeManager;
interface
uses
  xmldom, XMLIntf, msxmldom, XMLDoc, SysUtils, DateUtils, Classes, Dialogs,
[...]

type
  TXmlNodeManager = class;

  TXmlFileManager = class
  private
    [...]
    xmEnp: TXmlEnpManager;
    xmEnpInicial: TXmlEnpManager;
    xmEnpFinal: TXmlEnpManager;
[...]

  TXmlNodeManager = class
   protected
        sgyIterator: Integer;
        sgyContext: TXmlFileManager;
        sgyAttributes: TStringList;
        sgyNode: IXMLNode;
[...]
end.