Creating a QList from a plain array

Question

I have this

Struct values[] = {
  { a, b },
  { c, d }
};

And I just want to create a QList out of it

QList<Struct> ql(values + 0, values + 2);

But for some reason, QList has no suitable constructor and seemingly no suitable insert function. How does this work? I'm on Qt4.6.

Answer 1

One solution would be to first create an std::list and then convert that into a QList:

QList<Struct> ql = 
    QList<Struct>::fromStdList(std::list<Struct>(values + 0, values + 2));

However, that would incurs two copies of the array content instead of just one.

The other solution is to use std::copy along with a back_inserter:

QList<Struct> ql;
ql.reserve(2);
std::copy(values + 0, values + 2, std::back_inserter(ql));

If you use an array just to have an easy way to initialize the QList, you could perhaps use the insertion operator instead (assuming Struct defines the proper constructor):

QList<Struct> ql;
ql << Struct(a, b)
   << Struct(c, d);

Answer 2

Use fromStdList() static member function as:

std::list<Struct> stdList(values + 0, values + 2);
QList<Struct> ql = QList<Struct>::fromStdList(stdList);

Or just in one line:

QList<Struct> ql = QList<Struct>::fromStdList(std::list<Struct>(values + 0, values + 2));