Dynamically create multiple layouts

[SamuelAdesola]

@JonB How can i go about creating multiple objects. I tried using vectors of object but not working.

[mpergand]

@SamuelAdesola
Do all your layouts contain the same bunch of widgets ?

[SamuelAdesola]

@mpergand Yes
The same set of widgets repeated in a certain number of times based on the user's input

[mpergand]

@SamuelAdesola
One possibility:

const int LayoutCount=7;
struct LayoutWidgets
{
        QHBoxLayout* layout; 
        QLabel*     CourseCodeLabel;
        QLineEdit*  CourseCodeLineEdit;
        QLabel*     CourseGradeLabel;
        QComboBox*  CourseGradeComboBox;
};

LayoutWidgets layoutArray[LayoutCount];

...
// populate layoutArray
for(int i=0; i<LayoutCount; i++)
    {
    QHBoxLayout* layout=this->findChild<QHBoxLayout*>(QString("horizontalLayout_%1").arg(i+1));
    if(layout==nullptr)
        {
        // not found
        continue;
        }
    layoutArray[i].layout=layout;
    layoutArray[i].CourseCodeLabel=new QLabel;
    layoutArray[i].CourseCodeLineEdit=new QLineEdit;
    layoutArray[i].CourseGradeLabel=new QLabel;
    layoutArray[i].CourseGradeComboBox=new QComboBox;
    
    // populate QLayout
    layout->addWidget(layoutArray[i].CourseCodeLabel);
    layout->addWidget(layoutArray[i].CourseCodeLineEdit);
    layout->addWidget(layoutArray[i].CourseGradeLabel);
    layout->addWidget(layoutArray[i].CourseGradeComboBox);
    }

Of course not tested !

[SamuelAdesola]

@mpergand
Thanks
I will implement this and get back to you.

[mpergand]

@SamuelAdesola

repeated in a certain number of times based on the user's input

the number of layouts is not fixed ?

[SamuelAdesola]

@mpergand said in Dynamically create multiple layouts:

const int LayoutCount=7;
struct LayoutWidgets
{
QHBoxLayout* layout;
QLabel* CourseCodeLabel;
QLineEdit* CourseCodeLineEdit;
QLabel* CourseGradeLabel;
QComboBox* CourseGradeComboBox;
};

LayoutWidgets layoutArray[LayoutCount];

...
// populate layoutArray
for(int i=0; i<LayoutCount; i++)
{
QHBoxLayout* layout=this->findChild<QHBoxLayout*>(QString("horizontalLayout_%1").arg(i+1));
if(layout==nullptr)
{
// not found
continue;
}
layoutArray[i].layout=layout;
layoutArray[i].CourseCodeLabel=new QLabel;
layoutArray[i].CourseCodeLineEdit=new QLineEdit;
layoutArray[i].CourseGradeLabel=new QLabel;
layoutArray[i].CourseGradeComboBox=new QComboBox;

// populate QLayout
layout->addWidget(layoutArray[i].CourseCodeLabel);
layout->addWidget(layoutArray[i].CourseCodeLineEdit);
layout->addWidget(layoutArray[i].CourseGradeLabel);
layout->addWidget(layoutArray[i].CourseGradeComboBox);
}

It worked Perfectly. Thanks very much

[SamuelAdesola]

@mpergand Max is 15, I created the 15 spaces in the from ui. The number created on at runtime depends on the user input

[SGaist]

Hi,

Since you have a dynamic number of objects, you should use a QVector to hold the exact number of them.

That will simplify your code and memory handling.

[mpergand]

@SamuelAdesola
As @SGaist said use QVector:

LayoutWidgets layoutArray[LayoutCount];
QVector<LayoutWidgets> layoutArray;

then first create a LayoutWidgets instance in the loop:
for(int i=0; i<LayoutCount; i++)
{
layoutArray<<LayoutWidgets;
....

Max is 15, I created the 15 spaces in the from ui

Why not create this layouts in code as well?

[SamuelAdesola]

@mpergand
I successfully implemented this but came across a problem along the way, i have tried solving it but i am still not getting it.

After dynamically creating the objects using QVector, I wanted to access the element of the object using another funtion when a button is clicked but the program keeps crashing.

How can i access these elements in another function?

I want to be able to do something like

qDebug() << layoutArray[1].CourseCodeLabel->text();

[mpergand]

@SamuelAdesola
Use the debugger and show us the stack trace.

[jonezzpeterr]

I will implement this and get back to you.

[JonB]

@SamuelAdesola
If you have code like layoutArray[1].CourseCodeLabel->text() which crashes you will doubtless find that layoutArray[1] does not exist or layoutArray[1]->CourseCodeLabel is null/not valid. Which a stack trace should indeed reveal.

[SamuelAdesola]

@jonezzpeterr
Ok, I'll be looking forward to it

[SamuelAdesola]

@JonB
Can I make layoutArray a global variable so if I assign it in a function, I can access it in another function. One function is to show the user the forms layouts and another is to use the inputed data to do some calculations. I should have put them in same function but the calculation aspect automatically use the empty fields when a button is press. There are 2 buttons, one to show the user the fields and the other to make use of the inputed data for some calculations.

[JonB]

@SamuelAdesola
Make it a class member variable, rather than global, and you can access it in any class method. The fact that it is array is not relevant. And btw if it's a plain C array better use a QVector, say.

[SamuelAdesola]

@JonB @mpergand @jonezzpeterr @SGaist

Thanks very much for the support, I think i have achieve quite a lot of those giving tough time.

As @SGaist said I am using QVector and as @JonB said i declare it as a class member variable

QVector<LayoutWidgets> layoutArray;

Because the size will be set at run time base on user input, i resize the vector in a function

layoutArray.resize(LayoutCount);

and i am able to make calls to my class setters to set the values in layoutArray and use another getter function to access the set values