If you are new to C++ then some of the compiler errors can be a bit confusing and daunting at first. For example if the compiler given you an expected primary-expression error (e.g. expected primary-expression before ‘.’ token), at face value it does not make sense.
void RGBViewer::accept() {
QMessageBox::information(this, "Button Clicked", "You clicked OK", QMessageBox::Ok);
QColor color = QColor(Ui_RGBViewerClass.spinBoxRed->value(),
Ui_RGBViewerClass.spinBoxGreen->value(),
Ui_RGBViewerClass.spinBoxBlue->value(),
255);
qDebug() << color;
QBrush brush(color);
brush.setStyle(Qt::SolidPattern);
ui.graphicsView->setBackgroundBrush(brush);
ui.graphicsView->backgroundBrush();
}
When I compile the above code snippet, I get the following error from the compiler:
rgbviewer.cpp: In member function ‘virtual void RGBViewer::accept()’:
rgbviewer.cpp:19: error: expected primary-expression before ‘(’ token
rgbviewer.cpp:19: error: expected primary-expression before ‘.’ token
rgbviewer.cpp:20: error: expected primary-expression before ‘.’ token
rgbviewer.cpp:21: error: expected primary-expression before ‘.’ token
All this means is that I need to initialize the type ‘Ui_RGBViewerClass’ as the compiler does not understand it. In other words, I need to use a new.
Here is the ‘fixed’ version below of the same code snippet.
Ui::RGBViewerClass ui; //Defined in the header; shown here for completness
void RGBViewer::accept() {
QMessageBox::information(this, "Button Clicked", "You clicked OK", QMessageBox::Ok);
QColor color = QColor(ui.spinBoxRed->value(),
ui.spinBoxGreen->value(),
ui.spinBoxBlue->value(),
255);
qDebug() << color;
QBrush brush(color);
brush.setStyle(Qt::SolidPattern);
ui.graphicsView->setBackgroundBrush(brush);
ui.graphicsView->backgroundBrush();
}
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If you want to copy one string to another, one option can be something like this.
[sourcecode lang="cpp" toolbar="false"]
void mycopy(char *p, char *q) {
int len = strlen(q);
for(int i=0; i<=len; i++)
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}
[/sourcecode]
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[sourcecode lang="cpp" toolbar="false"]
v... - January 10, 2010 -- ‘QPainter painter’ has initialiser but incomplete type (0)
If you ever got an error something like [some-class] has initialiser but incomplete type, it basically means the compiler cannot understand the type and you need to add the include for it.
[sourcecode lang="cpp" toolbar="false"]
QPixmap pixmap(20,10);
pixmap.fill(Qt::white);
QPainter painter(&pixmap);
QPen pen(Qt::blue);
[/sourcecode]
Take the code snipped above when you compile it you might get an error something along the lines of the following for line 4.
‘QPainter painter’ ...
Tags: .code
