我如何传递一个函数引用在C ++ / CLI的报告回调？

Question

我有一些代码，处理数据文件，当它遇到麻烦报告错误，但我有麻烦工作如何给我的课的回调函数。这里是那种我想要实现的事情的一个简单的例子：

public delegate void Reporter( System::String^ stringToReport );

/// <summary>
/// Simple file handler with callback options on error
/// </summary>
public ref class MyFileHandler
{
private:
    Reporter^ m_reporter;

    void ReportError(String^ error)
    {
        if( m_reporter )
        {
            m_reporter( error );
        }
    }

public:
    MyFileHandler()
    {

    }

    void SetErrorReporter( Reporter^ reporter )
    {
        m_reporter = reporter;
    }

    bool FailingOperation()
    {
        return false;
    }

    bool GetData()
    {
        bool succeeded = false;

        // Do some operation that fails
        succeeded = FailingOperation();

        if( succeeded == false )
        {
            ReportError( "Gah, something bad happened!" );
        }

    }
};


public ref class MyFileLoader
{
private:
    MyFileHandler m_mfh;

    void ErrorHandler(String^ errorMsg)
    {
        System::Windows::Forms::MessageBox::Show( errorMsg );
    }

public:
    MyFileLoader()
    {
        m_mfh.SetErrorReporter( &CallbackFunctionTests::MyFileLoader::ErrorHandler );
    }
};

...其具有一个问题：

1>CallbackTest.h(131) : error C3374: can't take address of 'CallbackFunctionTests::MyFileLoader::ErrorHandler' unless creating delegate instance

所以我得到的印象，我误用或误解的东西。也许有实现这一目标的一个更好的办法？

Answer 1

您需要明确建立委托 - 你需要通过相关的实例 - 在你的情况，this - 它：

m_mfh.SetErrorReporter(
    gcnew Reporter(this, &CallbackFunctionTests::MyFileLoader::ErrorHandler));

Answer 2

在的情况下任何人的兴趣，这里的最终（工作）代码：

public delegate void Reporter( System::String^ stringToReport );

/// <summary>
/// Simple file handler with callback options on error
/// </summary>
public ref class MyFileHandler
{
private:
    Reporter^ m_reporter;

    void ReportError(String^ error)
    {
        if( m_reporter )
        {
            m_reporter( error );
        }
    }

public:
    MyFileHandler()
    {

    }

    void SetErrorReporter( Reporter^ reporter )
    {
        m_reporter = reporter;
    }

    bool FailingOperation()
    {
        return false;
    }

    bool GetData()
    {
        bool succeeded = false;

        // Do some operation that fails
        succeeded = FailingOperation();

        if( succeeded == false )
        {
            ReportError( "Gah, something bad happened!" );
        }

        return succeeded;
    }
};


public ref class MyFileLoader
{
private:
    MyFileHandler m_mfh;

    void ErrorHandler(String^ errorMsg)
    {
        System::Windows::Forms::MessageBox::Show( errorMsg );
    }

public:
    MyFileLoader()
    {
        m_mfh.SetErrorReporter( gcnew Reporter(this, &CallbackFunctionTests::MyFileLoader::ErrorHandler) );
    }
};