c++ - Qt - invoke slot only when both signals are emitted -

i have 3 processes: a, b , final. final depends on both a , b , can/must updated when both a , b updated. there signal datachanged updates both a , b (and final well). slots update_a , update_b invoked other signals.

mainwindow::mainwindow(qwidget* parent)   : qmainwindow(parent),     pa(false),     pb(false) { ... connect(this, &mainwindow::xchanged, this, &mainwindow::update_a); connect(this, &mainwindow::ychanged, this, &mainwindow::update_b); connect(myobj, &myclass::datachanged, this, &mainwindow::update_a); connect(myobj, &myclass::datachanged, this, &mainwindow::update_b); connect(this, &mainwindow::a_updated, this, &mainwindow::update_final); connect(this, &mainwindow::b_updated, this, &mainwindow::update_final); ... }  void mainwindow::update_a() {   if (!this.pa) {     //    }   this.pa = true;   emit a_updated; }  void mainwindow::update_b() {   if (!this.pb) {     //    }   this.pb = true;   emit b_updated; }  void mainwindow::update_final() {   if (this.pa && this.pb) {     //     this.pa = false;     this.pb = false;   } } 

is there anyway combine signals , operator rid off using pa , pb? or did use signals , slots in wrong way?

edit: sorry forgot mention: update_a , update_b invoked other signals, have keep them separated slots. , updated question , code above.

no, there's no supplied signal combination operators in qt. you'll need implement own, have done, or like:

void mainwindow::update_a() {   if (!pa) {     //    }   pa = true;   if (pa && pb)       emit ab_updated(); } 

if use pattern frequently, may worthwhile define object class sole responsibility of logical operations on signal sequences. complete, want 'a before b' , 'a after b' operators too.