marshal_as、字符串和字段与属性

发布于 2024-09-18 00:28:37 字数 1215 浏览 5 评论 0原文

include "stdafx.h"

#include <string>
#include <msclr/marshal_cppstd.h>

ref class Test {
    System::String^ text;
    void Method() {
        std::string f = msclr::interop::marshal_as<std::string>(text); // line 8
    }
};

使用 VS2008 编译时这段代码给出：

.\test.cpp(8) : error C2665: 'msclr::interop::marshal_as' : none of the 3 overloads could convert all the argument types
        f:\programy\vs9\vc\include\msclr\marshal.h(153): could be '_To_Type msclr::interop::marshal_as<std::string>(const char [])'
        with
        [
            _To_Type=std::string
        ]
        f:\programy\vs9\vc\include\msclr\marshal.h(160): or       '_To_Type msclr::interop::marshal_as<std::string>(const wchar_t [])'
        with
        [
            _To_Type=std::string
        ]
        f:\Programy\VS9\VC\include\msclr/marshal_cppstd.h(35): or       'std::string msclr::interop::marshal_as<std::string,System::String^>(System::String ^const &)'
        while trying to match the argument list '(System::String ^)'

但是当我将字段更改为属性时：

    property System::String^ text;

那么这段代码编译时没有错误。为什么？

原文

include "stdafx.h"

#include <string>
#include <msclr/marshal_cppstd.h>

ref class Test {
    System::String^ text;
    void Method() {
        std::string f = msclr::interop::marshal_as<std::string>(text); // line 8
    }
};

This code when compiled with VS2008 gives:

.\test.cpp(8) : error C2665: 'msclr::interop::marshal_as' : none of the 3 overloads could convert all the argument types
        f:\programy\vs9\vc\include\msclr\marshal.h(153): could be '_To_Type msclr::interop::marshal_as<std::string>(const char [])'
        with
        [
            _To_Type=std::string
        ]
        f:\programy\vs9\vc\include\msclr\marshal.h(160): or       '_To_Type msclr::interop::marshal_as<std::string>(const wchar_t [])'
        with
        [
            _To_Type=std::string
        ]
        f:\Programy\VS9\VC\include\msclr/marshal_cppstd.h(35): or       'std::string msclr::interop::marshal_as<std::string,System::String^>(System::String ^const &)'
        while trying to match the argument list '(System::String ^)'

But when I change the field into property:

    property System::String^ text;

then this code compiles without errors. Why?

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留一抹残留的笑 2024-09-25 00:28:37

解决方法是制作如下副本：

ref class Test {
    System::String^ text;
    void Method() {
        System::String^ workaround = text;
        std::string f = msclr::interop::marshal_as<std::string>(workaround);
    }
};

A workaround is to make a copy like this:

ref class Test {
    System::String^ text;
    void Method() {
        System::String^ workaround = text;
        std::string f = msclr::interop::marshal_as<std::string>(workaround);
    }
};

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简单气质女生网名 2024-09-25 00:28:37

Bug，在VS2010中修复。反馈项目在这里。

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葬花如无物 2024-09-25 00:28:37

我经常使用这个片段，声明一个新变量太混乱了。然而这也有效：

msclr::interop::marshal_as<std::string>(gcnew String(string_to_be_converted))

另一个对我有用的选择是这个小模板。它不仅解决了这里讨论的错误，还修复了 marshal_as 损坏的另一个问题，即它不适用于 nullptr 输入。但实际上 nullptr System::String 的一个很好的 C++ 翻译是 .empty() std::string()。这是模板：

template<typename ToType, typename FromType>
inline ToType frum_cast(FromType s)
{
    if (s == nullptr)
        return ToType();
    return msclr::interop::marshal_as<ToType>(s);
}

I'm using this snippet a lot, and it's too much clutter to declare a new variable. However this works too:

msclr::interop::marshal_as<std::string>(gcnew String(string_to_be_converted))

Another option that works for me is this little template. Not only does it solve the bug discussed here, it also fixes another thing that's broken with marshal_as, namely that it does not work for nullptr input. But actually a good c++ translation for a nullptr System::String would be an .empty() std::string(). Here is the template:

template<typename ToType, typename FromType>
inline ToType frum_cast(FromType s)
{
    if (s == nullptr)
        return ToType();
    return msclr::interop::marshal_as<ToType>(s);
}

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~没有更多了~