how connection variable in functin with spinBox

[Zlatomir]

Isn't it better to put the 'i' variable in the class definition? (not a local variable to that function)
And declare a function (a slot, with "public slots:" access specifier) and that function will look like:

void  YourClass::set_i(double input) { i = input;} //i is your member variable i

void  YourClass::set_i(double input) { i = input;} //i is your member variable i

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and connect this slot with the SpinBox valueChanged signal:
(in your class constructor if the spinbox2 is member of the same class!)

connect(spinBox2,SIGNAL(valueChanged(double)), this, SLOT(set_i(double));

connect(spinBox2,SIGNAL(valueChanged(double)), this, SLOT(set_i(double));

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Note: You can do it with double or int, but the QSpinBox doesn't have a valueChanged(double) only int
QDoubleSpinBox has valueChanged(double) not int

And we can't create a complete design, we can only give you advices, because we don't know the actual problem (don't even know the design of your class)

[sherbs]

As others have mentioned, you need to spend some time doing your homework:

http://doc.trolltech.com/4.6/signalsandslots.html

Read through this documentation and you should easily be able to accomplish what you want to do... As of now, your design/code reflects a fairly fundamental misunderstanding of how Qt works.

It will be very difficult to help you otherwise.

[Sergey19]

Isn't it better to put the 'i' variable in the class definition? (not a local variable to that function)
And declare a function (a slot, with "public slots:" access specifier) and that function will look like:

void  YourClass::set_i(double input) { i = input;} //i is your member variable i

void  YourClass::set_i(double input) { i = input;} //i is your member variable i

To copy to clipboard, switch view to plain text mode 

and connect this slot with the SpinBox valueChanged signal:
(in your class constructor if the spinbox2 is member of the same class!)

connect(spinBox2,SIGNAL(valueChanged(double)), this, SLOT(set_i(double));

connect(spinBox2,SIGNAL(valueChanged(double)), this, SLOT(set_i(double));

To copy to clipboard, switch view to plain text mode 

Note: You can do it with double or int, but the QSpinBox doesn't have a valueChanged(double) only int
QDoubleSpinBox has valueChanged(double) not int

And we can't create a complete design, we can only give you advices, because we don't know the actual problem (don't even know the design of your class)

I create a line ....And I want when user change value in spinBox this line move left or right .