Inserting dynamic-allocated objects into QHash

Question

I have a QHash<QString, myClass*> objects and in order to insert I did the following:

myClass *value = objects.value(key);
    if(!value) {
        value = new myClass;
        objects.insert(key, value);
    }

Is this right approach?

Answer 1

Your solution is one of several possible correct approaches.

I usually do it like this as I find it a bit more readable

if( !objects.contains( key ) )
{
    objects.insert( key, new MyClass );
}
MyClass* value = objects.value( key);

As already suggested by Marek R, you can use smart pointers for easier memory management:

QHash< QString, QSharedPointer< MyClass > > objects;
// ...
QSharedPointer< MyClass > value = objects.value( key );

Since C++11, I prefer using std::shared_ptr.

This allows you to not care about delete calls; just make sure you always use QSharedPointer< MyClass > instead of MyClass* everywhere. Also, you mustn't use shared pointers for QObject subclasses which have a parent, as the parent object will store a regular pointer for it.