error C2064: term does not evaluate to a function taking 0 arguments

Question

everyone! I maintain a group of channel data in a map container, from which an individual channel data can be accessed by its channle name. With regards to this, I write a simple function GetIRChannelData (please see the following code). When compliing, the statement pusIRChannelData = cit->second(); throwed an error, which read

error C2064: term does not evaluate to a function taking 0 arguments

All the function to do is nothing but to search for a given channel name/ID in the map container, and assign it data pointer to a temporal pointer if found. Would you please show me what's wrong?

const Array2D<unsigned short>* GetIRChannelData(std::string sChannelName) const
{   
    const Array2D<unsigned short>* pusIRChannelData = NULL;

    for (std::map<std::string, Array2D<unsigned short>* >::const_iterator cit =    m_usIRDataPool.begin(); cit != m_usIRDataPool.end(); ++cit) 
    {   
        std::string sKey = cit->first; 

        if (sKey == sChannelName)
        {   
           pusIRChannelData = cit->second(); // Error occurred on this line
           break;
        }
    }

    return pusIRChannelData;
}

Answer 1

The error message is pretty clear... you call a function that doesn't exist. map::iterator points to a std::pair, which has two member objects, first and second. Note that these are not functions. Remove the () from the line in question and the error should go away.

Answer 2

It looks like cit->second doesn't identify a function pointer. The definition of your iterator claims it's a pointer to (Array2D<unsigned short>); pusIRChannelData is an (Array2D *), so you probably want cit->second instead of cit->second() (which tries to invoke your (Array2D *) as a function).