将代码从 Delphi 翻译成 C++ Builder 10.3

Question

parsing 有一个库。

我在项目中添加了ALXmlDoc.pas，C++Builder创建了ALXmlDoc.hpp 在 ALXmlDoc.pas 行 177,178 中：

property Nodes [const Name: AnsiString]: TALXMLNode read GetNodeByName; default;
property Nodes [const Index: integer]: TALXMLNode read GetNodeByIndex; default;

在ALXmlDoc.hpp中：

__property TALXMLNode * Nodes [const System :: AnsiString Name] = {read = GetNodeByName / *, default */};
__property TALXMLNode * Nodes [const int Index] = {read = GetNodeByIndex};

我收到关于重复的错误 - 如何解决？

在 .pas 行 705

property OnParseText: TAlXMLParseTextEvent read FonParseText Write FonParseText; // [added from TXMLDocument]

在ALXmlDoc.hpp中：

__property _di_TAlXMLParseTextEvent OnParseText = {read = FonParseText, write = FonParseText};
__interface TAlXMLParseTextEvent: public System :: IInterface
{
    virtual void __fastcall Invoke (System :: TObject * Sender, const System :: AnsiString Path, const System :: AnsiString Str) = 0;
};
     
private:
    _di_TAlXMLParseTextEvent FonParseText;
protected:
    void __fastcall DoParseText (const System :: AnsiString Path, const System :: AnsiString Str);

在我的 Unit1.h 中：

void __fastcall OnParseText (System :: TObject * Sender, const System :: AnsiString Path, const System :: AnsiString Str);

在我的 Unit1.cpp 中：

void __fastcall TForm1 :: OnParseText (System :: TObject * Sender, const System :: AnsiString Path, const System :: AnsiString Str)
{
    ShowMessage(Str); 
}
// ------------------------------------------------ ---------------------------
void __fastcall TForm1 :: Button1Click (TObject * Sender)
{
    TALXMLDocument * aXMLDocument = new TALXMLDocument ("root");
    aXMLDocument-> OnParseText = OnParseText;
}

我得到一个错误：

[bcc32 Error] Unit1.cpp (30): E2235 Member function must be called or its address taken

如何申报活动？

Answer 1

在 C++ 中，数组属性不能仅在其索引类型上重载。因此，您将不得不重命名其中一个有问题的属性，没有其他选择。然后我建议你向库作者提交一份报告，要求使库对 C++ 用户更友好。

在 Delphi 代码中，TAlXMLParseTextEvent 是对 anonymous method:

的引用

TAlXMLParseTextEvent = reference to procedure (Sender: TObject; const Path, Str: AnsiString);

这就是它在 C++ 端被翻译成 __interface 的原因（因为匿名方法实际上是使用接口在幕后实现的）。 Delphi 风格的匿名方法需要在 C++ 中进行额外处理，如 Embarcadero 的 DocWiki 中所述：

How to Handle Delphi Anonymous Methods in C++

Under the cover, Delphi implements anonymous methods types (also known as method references) via an interface that implements an Invoke(...) method.

So a method that takes a method reference parameter in Delphi is exposed to C++ as a method that takes an interface.

因此，您的 C++ 代码需要做更多类似的事情：

struct TParseTextMethod
{
    void operator()(TObject *Sender, const AnsiString Path, const AnsiString Str)
    {
        ShowMessage(Str); 
    }
};
//------------------------------------------------ ---------------------------
void __fastcall TForm1::Button1Click(TObject *Sender)
{
    TALXMLDocument *aXMLDocument = new TALXMLDocument("root");

    // the TMethodRef functor is defined in the documentation,
    // you can copy/paste it as-is into your code...
    typedef TMethodRef<TAlXMLParseTextEvent,
                     TParseTextMethod,
                     void,
                     TObject *Sender,
                     const AnsiString,
                     const AnsiString> MyMethRef;

    aXMLDocument->OnParseText = _di_TAlXMLParseTextEvent(new MyMethRef(TParseTextMethod()));
}

或者，您可以通过不使用 TMethodRef 包装器（参见 Inheritance and Interfaces and Implementing Interfaces）来进一步简化仿函数的使用：

class TParseTextMethod : public TCppInterfacedObject<TAlXMLParseTextEvent>
{
public:
    TParseTextMethod() {}
    INTFOBJECT_IMPL_IUNKNOWN(TInterfacedObject);

    void __fastcall Invoke(TObject *Sender, const AnsiString Path, const AnsiString Str)
    {
        ShowMessage(Str); 
    }
};
//------------------------------------------------ ---------------------------
void __fastcall TForm1::Button1Click(TObject *Sender)
{
    TALXMLDocument *aXMLDocument = new TALXMLDocument("root");

    aXMLDocument->OnParseText = _di_TAlXMLParseTextEvent(new TParseTextMethod());
}

或者，如果您想按原样继续使用 OnParseText() 方法，则必须将它包装在一个仿函数中，例如：

void __fastcall TForm1::OnParseText(TObject *Sender, const AnsiString Path, const AnsiString Str)
{
    ShowMessage(Str); 
}
//------------------------------------------------ ---------------------------
typedef void __fastcall (__closure *TAlXMLParseTextMethod)(TObject *Sender, const AnsiString Path, const AnsiString Str);

struct TParseTextMethod
{
    TAlXMLParseTextMethod Method;

    TParseTextMethod(TAlXMLParseTextMethod aMethod) : Method(aMethod) {}

    void operator()(TObject *Sender, const AnsiString Path, const AnsiString Str)
    {
        Method(Sender, Path, Str);
    }
};
//------------------------------------------------ ---------------------------
void __fastcall TForm1::Button1Click(TObject *Sender)
{
    TALXMLDocument *aXMLDocument = new TALXMLDocument("root");

    typedef TMethodRef<TAlXMLParseTextEvent,
                     TParseTextMethod,
                     void,
                     TObject *Sender,
                     const AnsiString,
                     const AnsiString> MyMethRef;

    aXMLDocument->OnParseText = _di_TAlXMLParseTextEvent(new MyMethRef(TParseTextMethod(&OnParseText)));
}

或：

void __fastcall TForm1::OnParseText(TObject *Sender, const AnsiString Path, const AnsiString Str)
{
    ShowMessage(Str); 
}
//------------------------------------------------ ---------------------------
typedef void __fastcall (__closure *TAlXMLParseTextMethod)(TObject *Sender, const AnsiString Path, const AnsiString Str);

class TParseTextMethod : public TCppInterfacedObject<TAlXMLParseTextEvent>
{
public:
    TAlXMLParseTextMethod Method;

    TParseTextMethod(TAlXMLParseTextMethod aMethod) : Method(aMethod) {}
    INTFOBJECT_IMPL_IUNKNOWN(TInterfacedObject);

    void __fastcall Invoke(TObject *Sender, const AnsiString Path, const AnsiString Str)
    {
        Method(Sender, Path, Str);
    }
};
//------------------------------------------------ ---------------------------
void __fastcall TForm1::Button1Click(TObject *Sender)
{
    TALXMLDocument *aXMLDocument = new TALXMLDocument("root");

    aXMLDocument->OnParseText = _di_TAlXMLParseTextEvent(new TParseTextMethod(&OnParseText));
}

或者，如果您使用 Clang-based compilers then you can use a C++ style lambda 之一而不是函子：

void __fastcall TForm1::Button1Click(TObject *Sender)
{
    TALXMLDocument *aXMLDocument = new TALXMLDocument("root");
    aXMLDocument->OnParseText = [](TObject*, const AnsiString, const AnsiString Str) {
        ShowMessage(Str);
    };
}

或：

void __fastcall TForm1::OnParseText(TObject *Sender, const AnsiString Path, const AnsiString Str)
{
    ShowMessage(Str); 
}
//------------------------------------------------ ---------------------------
void __fastcall TForm1::Button1Click(TObject *Sender)
{
    TALXMLDocument *aXMLDocument = new TALXMLDocument("root");
    aXMLDocument->OnParseText = [this](TObject *Sender, const AnsiString Path, const AnsiString Str) {
        OnParseText(Sender, Path, Str);
    };
}

将代码从 Delphi 翻译成 C++ Builder 10.3

Translate code from Delphi to C ++ Builder 10.3

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