how connection variable in functin with spinBox

[Sergey19]

Good afternoon !
I am beginner in qt.I have a problem .How connection variable i in function with my spinBox.
This my function :

void DataPlot::insertCurve(Qt::Orientation o,
const QColor &c, double base)
{
QwtPlotCurve *curve = new QwtPlotCurve();
curve->setPen(QPen(Qt::blue,3));
 
 
double i ;
double x[10];
double y[sizeof(x) / sizeof(x[0])];
 
for ( uint k = 0; k < sizeof(x) / sizeof(x[0]); k++ )
{
double v = i+k * 1.5;
if ( o == Qt::Horizontal )
{
x[k] = v;
y[k] = base;
}
else
{
x[k] = base;
y[k] = v;
}
}
 
curve->setData(x, y, sizeof(x) / sizeof(x[0]));
curve->attach(this);
}

void DataPlot::insertCurve(Qt::Orientation o,
const QColor &c, double base)
{
QwtPlotCurve *curve = new QwtPlotCurve();
curve->setPen(QPen(Qt::blue,3));


double i ;
double x[10];
double y[sizeof(x) / sizeof(x[0])];

for ( uint k = 0; k < sizeof(x) / sizeof(x[0]); k++ )
{
double v = i+k * 1.5;
if ( o == Qt::Horizontal )
{
x[k] = v;
y[k] = base;
}
else
{
x[k] = base;
y[k] = v;
}
}

curve->setData(x, y, sizeof(x) / sizeof(x[0]));
curve->attach(this);
}

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[Zlatomir]

You want the i variable to get the spin box value?Sorry, but i don't understand what you meant by connection.

[GreenScape]

double y[sizeof(x) / sizeof(x[0])];

double y[sizeof(x) / sizeof(x[0])];

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looking wroong. what is the reason for dividing size of array on size of array element?

[Zlatomir]

@GreenScape: It's the C style way of find out the size (number of elements) of an C-style array, but you are right it's completely useless (since the array size is known to be 10)

[GreenScape]

no way man! sizeof(x) returns 10, but not 40! and sizeof(x) / sizeof(x[0]) == 2.5 ! maybe the old C-style way to find out the array size you mean? then sizeof(x) * sizeof(x[0]), because when array is local and not dynamucally allocated, sizeof() allways returns number of elements.

[Zlatomir]

@GreenScape: I have to contradict you: qDebug() << sizeof(x); //should print 40 in our case, and if you make 40/4 you get 10 (number of elements, the multiply wouldn't make sense)

I think (not 100% positive about this one)... it might fail if you use a pointer: like int *ptr = new int[10]; sizeof(ptr); returns 4(size of a pointer)

Anyway in this particular case it is not necessary because the number of elements it's known.

[Sergey19]

Execuse me for me .I want that variable i changed with spinBox.help me,please )

[Zlatomir]

Is the function: void DataPlot::insertCurve(Qt::Orientation o, const QColor &c, double base) in the same object with QSpinBox?
If yes, just use:

double i = spinBoxObjectName.value();

double i = spinBoxObjectName.value();

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If not tell us more "design" options, this function (void DataPlot::insertCurve(...)) you want to execute whenever the QSpinBox chage value, or just at some point (like user click a button, and the insertCurve executes with the current value of QSpinBox)
In this second case you will need signals and slots, but how to connect them depents on how/when you need the QSpinBox value, and in what object spinBox is... so we need a little more info.

And a little advice, you can use QVector (or std::vector) or QList instead of C-Style arrays, you have some facilities (like they know their size...)

[Sergey19]

Thank you very much ,but I want that user can change in spinbox my function redraw !)) Execuse me for my English !)

[Zlatomir]

QSpinBox has a signal called valueChanged witch is emitted when the value changes.

You can connect that signal to the slot/slots that update what you need (if you connect with the functions you wrote make sure that you declare them with "public slots:" access specifier)

LE: depends on your design, but another idea is to have an int (or double) variable as a member in your class and write setter and getter functions for that (declare the setter function slot and connect the valueChanged signal to the setter slot <witch updates the member variable's value)

[Sergey19]

how write this coonect! Execuse maybe we write examples !))