std::initializer_list<T> as constructor parameter and uniform initialization syntax

Question

For some time now I use C++11 uniform initialization syntax {} to initialize all my variables.

Right now I want to initialize a QVector<int> with a specific size, so I need to call the QVector(int size) constructor (doc here).

However, QVector also has the following constructor: QVector(std::initializer_list<T> args)

So when I initialize my variable like this: QVector<int> foo{ 100 };, it doesn't initialize my QVector with a size of 100 elements, but rather calls the other constructor which constructs a QVector with one element of value 100.

How can I call the QVector(int size) constructor but still use the uniform initialization syntax?

Answer 1

You are trying to do the thing which is impossible. The only way to get constructor with specific size is using () brackets:

QVector<int> v(100);

The reason is that otherwise it would cause ambiguity. Compiler would not know what is

QVector<int> v{100};

As it is done now, it always knows this is initializer list, i.e. inserts 1 element of 100, not 100 default elements.

Pay attention, this is not Qt-specific, in STL this works the same way.