Question

I find some code sample with these oddl lines

QList<TDataXml *> *newXMLData = input->getValue<QList<TDataXml *>>();
    if(newXMLData) 
    {
        // do things
    }

I dont understand if(newXMLData). This is a QList. When should statement be true or false? Why not use Qt isEmpty() method instead?

Thanks

Answer 1

if(newXMLData) checks for nullity, because newXMLData is a pointer, and therefore it could point to no object, in which case it’s value is nullptr (or NULL in C++03).

If newXMLData is not nullptr, then it will be true and the if-block will execute, otherwise false and if-block will not execute.

It is same as (C++11):

if(newXMLData != nullptr) //or if(newXMLData != NULL) in pre C++11
{
  //your code
}