Qt-creator's bug?

[Limer]

The first if (curColor == Qt::white) is ok for creator, but the second failed.

creator version is 4.8.0. (The latest qt release version).

This is a bug ? I don't verify it at older creator version.

[mrjj]

hi
Qt::darkGray is an enum / int.
So hence the the error.

[Limer]

@mrjj But why the first if(...) is ok!!!!

[mrjj]

@Limer
mine does for both

[Limer]

@mrjj Oh!!! I get it!!! C++ follows left-to-right. QColor can't convert to int implicitly!

------modified -------

QColor don't have operator int() { } conversion operator function, so the former is right, but the latter is wrong.

[Limer]

@mrjj NONONO,,,, My codes are: color == Qt::white and Qt::darkGray == color, their positions are opposite!

[mrjj]

Hi
I think what you want is
if (col == QColor(Qt::white) )
if (col == QColor(Qt::green) )

that should work.

[Limer]

@mrjj QColor has the convert function http://doc.qt.io/qt-5/qcolor.html#QColor-1

So I can just use color == Qt::white, their data types will convert to each other implicitly.

But qt-creator detects color == Qt::white is right, Qt::white == color is wrong.

[dheerendra]

In addition to what @mrjj is telling, there is concept called operator overloading in c++. I'm sure you aware of that. Following statement works

color == Qt::white

because QColor class has '=' (operator) overloaded. Look at the following function signature.

QColor &
operator=(Qt::GlobalColor color)

Where as there as there is no operator overaloading for (Qt::white == color )
Hence it does not work.

[mrjj]

@dheerendra
Hi
but is that not the assignment operator it has an overload of ?
And not the == (compare) operator ?

[dheerendra]

@mrjj both = and == are overloaded. In the current case it is ==.

[mrjj]

@dheerendra
Ah i missed that part :)