Can't initialize static QList?

Question

I get the following error:

Cube.cpp:10: error: expected initializer before ‘<<’ token

Here's the important parts of the header file:

#ifndef CUBE_H #define CUBE_H #include <cstdlib> #include <QtCore/QtCore> #include <iostream> #define YELLOW 0 #define RED 1 #define GREEN 2 #define ORANGE 3 #define BLUE 4 #define WHITE 5 using namespace std; class Cube { public: ... static QList<int> colorList; ... }; #endif

Here's the line that gives the error:

QList<int> Cube::colorList << YELLOW << RED << GREEN << ORANGE << BLUE << WHITE;

Lou Franco · Accepted Answer · 2010-12-01 02:33:16Z

You can't initialize an object with <<. The = that is usually there is not operator=() -- it's a special syntax that is essentially the same as calling a constructor.

Something like this might work

QList<int> Cube::colorList = EmptyList() << YELLOW << RED << GREEN << ORANGE << BLUE << WHITE;

where EmptyList() is

QList<int> EmptyList() { QList<int> list; return list; }

and is a copy construction of a list, and barring some optimization, a copy of the list that is created.

Thanks. I used something similar to what you've provided. Instead of empty list, I used new QList<int>() << ...; It seems to work. Do you see any potential issues in using this method?
Just that you are creating a list and then copying it. For such a short list and for just once in the app, I wouldn't worry about it.

Chubsdad · Accepted Answer · 2010-12-01 02:32:58Z

That line is not a initialization/definition of QList Cube::colorList. It is invoking insertion operator on an object which is not yet defined namely (QList Cube::colorList).

I don't know QT and hence can't comment on how to really initialize this class.

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