strange connect

[mickey]

I've problem: this connect get me a console error like as cannot connect check box to null::set(bool); but the SLOT starts; it works!Why?

FancyPopup::FancyPopup(myMainForm* parent, const char*  name ):
    QLabel( parent, name, WType_Popup ), _myw(parent){
connect (checkBox, SIGNAL(toggled(bool)), _myw, SLOT(set(bool)));

FancyPopup::FancyPopup(myMainForm* parent, const char*  name ):
    QLabel( parent, name, WType_Popup ), _myw(parent){
connect (checkBox, SIGNAL(toggled(bool)), _myw, SLOT(set(bool)));

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and why this connect get me a run time error:

connect (dial, SIGNAL(valueChanged(int)), _myw, SLOT(setValue(int)));

connect (dial, SIGNAL(valueChanged(int)), _myw, SLOT(setValue(int)));

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but this works:

connect (dial, SIGNAL(dialMoved(int)), _myw, SLOT(setValue(int)));

connect (dial, SIGNAL(dialMoved(int)), _myw, SLOT(setValue(int)));

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