Question

This seems to be a trivial question but I got hung on it for a few hours now (maybe too much Java killed my C++ braincells).

I have created a class that has the following constructor (i.e. no default constructor)

VACaptureSource::VACaptureSource( std::string inputType, std::string inputLocation ) {
    if( type == "" || location == "" ) {
    throw std::invalid_argument("Empty type or location in VACaptureSource()");
}
type = inputType;
location = inputLocation;

// Open the given media source using the appropriate OpenCV function.
if( type.compare("image") ) {
    frame = cvLoadImage( location.c_str() );
    if( !frame ) {
        throw std::runtime_error("error opening file");
    }
}
else {
    throw std::invalid_argument("Unknown input type in VACaptureSource()");
}

}

When I want to create an instance, I use

    // Create input data object
try {
    VACaptureSource input = VACaptureSource("image", "/home/cuneyt/workspace/testmedia/face_images/jhumpa_1.jpg");
}
catch( invalid_argument& ia ) {
    cerr << "FD Error: " << ia.what() << endl;
    usage(argv[0]);
}
catch( runtime_error& re ) {
    cerr << "FD Error: " << re.what() << endl;
    usage(argv[0]);
}

However, in this case the instance is local to this block and I can’t refer to it anywhere else. On the other hand, I can’t say

VACAptureSource input;

at the beginning of the program since there’s no default constructor.

What is the correct way to do this?

Thanks!

Answer 1

What about using a pointer (or some RAII version thereof)?

VACaptureSource* input = NULL;

try {
    input = new VACaptureSource(...);
} catch(...) {
    //error handling
}

//And, of course, at the end of the program
delete input;