.net - 如何通过引用传递函数以在 C++/CLI 中进行报告回调？

Question

我有一些代码可以处理数据文件并在遇到问题时报告错误，但是我无法弄清楚如何为我的类提供回调函数。这是我想要实现的事情的一个简单示例：

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 );
    }
};

...有一个问题：

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

所以我得到的印象是我误用或误解了一些东西。也许有更好的方法来实现这一目标？

Answer 1

您需要显式创建委托 - 并且您需要将关联的实例 - 在您的情况下this- 传递给它：

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

Answer 2

如果有人感兴趣，这是最终（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) );
    }
};