What is the right way to initialize a QList?

Question

What is the right way to initialize QList? I want to make this code shorter:

QSplitter splitter;
QList<int> list;
list.append(1);
list.append(1);
splitter.setSizes(list);

But when I use initialization from std::list, it doesn't seem be working:

splitter.setSizes(QList<int>::fromStdList(std::list<int>(1, 1)));

In latter case, the splitter seems to divide in ratio 1:0.

Solution 1

You could use the following code:

QList<int> list = QList<int>() << 1 << 1;

or initializer list with C++11:

QList<int> list({1, 1});

You can enable the latter with the -std=c++0x or -std=c++11 option for gcc. You will also need the relevant Qt version for that where initializer list support has been added to the QList constructor.

Solution 2

Never use the QList<int>() << 1 << 1; variant, as it's really slow. use always the list({1, 1}) variant.

source: https://www.angrycane.com.br/en/2018/06/19/speeding-up-cornercases/

Comments

[Thomas Ayoub]

Using Qt 5.2 it throws error: expected expression QList<int> list2({1, 1});

[László Papp]

@ꜱᴀᴍᴏᴛʜ: you need CONFIG+=c++11.

[Thomas Ayoub]

I though it was automatically enabled. Thank you !

[Jack]

What is that () in list({1,1})? it give me an syntax error. Should be QList<int> list {1, 1};?