Question

我的C++头盔有以下几条编码。

private:
    std::map<std::string, std::vector<std::vector<unsigned short> > > m_usIRDataPool;

public:
    std::vector<std::vector<unsigned short> >& IRChannelData(std::string sChannelName);

在其执行档案中,IRChannelData()的定义如下:

std::vector<std::vector<unsigned short> >& MyClass::IRChannelData(std::string sChannelName)
{   
    std::map<std::string, std::vector<std::vector<unsigned short> > >::iterator it = m_usIRDataPool.find( sChannelName );

    if ( it != m_usIRDataPool.end() )
    {  
       return it->second;
    }

  //  return ????; // How can I return?
}

因此,如果在<代码>m_usIRDataPool的地图集装箱内没有发现进入(病媒的探测器),将返回。

warning C4715:  MyClass::IRChannelData  : not all control paths return a value.

Answer 1

Return a bool indicating success/failure and return the address of the result vector via an "out" semantics parameter, or
throw an exception if no element found in map

Answer 2

如果找不到你重新找回的东西,则送回点和返回代码<0>>。

Answer 3

As you re returning the reference to something, you cannot declare an empty map on the function and then return it. What you can do is declare a variable in MyClass MyClass::emptyReturnMap of the same type you want to return std::vector<std::vector<unsigned short> >, and then return it. But if you re editing the contents of it (as the return is not const), you re gonna have to clear it on every call.

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