i created one pushbutton and label in myClass.cpp;

Qt Code: 
  1. QLabel *lbl=new QLabel();
  2. QPushButton *btn=new QPushButton("button");
  3.  
  4. ui->tableWidget->setCellWidget(0,0,lbl);
  5. ui->tableWidget->setCellWidget(0,1,btn);
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i want that: when i click button, calendar will open and when i click calendar, date will be written on label.
and i want to use signal & slot.

i created these functions:

Qt Code: 
  1. myClass.h
  2.  
  3. public:
  5.  
  6. public slots:
  7. void writeDate(QLabel *);
  8. void func();
  9. void openCal();
  10.  
  11. signals:
  12. void calClicked(QLabel *);
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Qt Code: 
  1. myClass.cpp
  2.  
  3. connect(btn,SIGNAL(clicked()),this,SLOT(openCal())); //it works
  4. connect(cal,SIGNAL(clicked(QDate)),this,SLOT(func()));//it works
  5. myClass *a,*b;
  6. QObject::connect(a, SIGNAL(calClicked(lbl)), b, SLOT(writeDate(lbl)));//it never works
  7.  
  8. void myClass::func()
  9. {
  10.       emit calClicked(lbl);
  11. }
  12.  
  13. void myClass::writeDate(QLabel *lbl)
  14. {
  15.     cal->close();
  16.     lbl->setText(cal->selectedDate());
  17. }
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but i always get error:QObject::connect: Cannot connect (null)::calClicked(lbl) to (null)::writeDate(lbl)


sorry for my english.