Solved How to efficiently create a QList with a single item in one statement?

[Asperamanca]

How do I create a QList containing a single item in a way I can use as input value for a method, e.g.

QHash<int,QList<int>> listHash;
listHash.insert(0,QList<int>(???)); //What kind of constructor or static creation method can I use here?

With std::vector it's easy:

QHash<int,std::vector<int>> vectorHash;
listHash.insert(0,std::vector<int>(1,5));  // Create vector with 1 item of value 5

However, I need to stick to an existing interface, so I have to use QList in my case...

[VRonin]

listHash.insert(0,QList<int>{5});

listHash.insert(0,QList<int>{5,4,3,2,1});

(if it doesn't work double the curly brakets)

[J.Hilk]

@asperamanca QList only offers the initializer list, QVector on the other hand, offers, like std::vector , a QVector(int size, const T &value) overload.

[Gojir4]

@asperamanca From c++11 you can initialize lists, vectors, maps, hashes, etc... using curly brackets:

    QHash<int,QList<int>> listHash;
    listHash.insert(0, {1});
    listHash.insert(1, QList<int>{1});
    listHash.insert(2, {1, 2, 3, 4});
    
    QHash<int,QList<int>> listHash2 = {
        {0, {1, 2, 3}},
        {1, {4, 5}},
        {2, {6, 7, 8}},
    };

[Asperamanca]

OK, I simplified the problem too much. I do not have a constant value for initialization, but an argument:

void addToHash(const int key, const int value)
{
   if (m_Hash.contains(key))
   {
      m_Hash[key].append(value);
   }
   else
   {
      m_Hash.insert(key,QList<int>{value});
   }
}

Here, the initializer list causes a compiler error:
'initializing': cannot convert from 'initializer list' to 'QList<int>'

EDIT:
And here I circumvent my original problem:

void addToHash(const int key, const int value)
{
   m_Hash[key].append(value);
}

...since operator[] default-constructs an entry if none exists.