Very new to QT

U7Development

Hi, i am very new to QT...

Do you use pointers to create and initialize properties?..
if not, do you create and initialize them on header or cpp file ?

Thanks

sierdzio

@U7Development said in Very new to QT:

Do you use pointers to create and initialize properties?..

Depends. You can store normal data in Q_PROPERTY, but you can store pointers, too. So this is really not something that can be answered definitely - all depends on your needs.

if not, do you create and initialize them on header or cpp file ?

Q_PROPERTY can only be used in a header file, or at least I have never seen it placed anywhere else.

I have no idea what you mean by "initialize" in context of a property.

mrjj

Hi and welcome to the forums
If you mean its initial value, don't forget there is a normal variable underneath the
Q_PROPERTY and you can do like you normally do.

class MyClass : public QObject
{
    Q_OBJECT
    Q_PROPERTY(Priority priority READ priority WRITE setPriority)
public:
    enum Priority { High, Low, VeryHigh, VeryLow };
    Q_ENUM(Priority)
    void setPriority(Priority priority)    {
        m_priority = priority;        
    }
    Priority priority() const    { return m_priority; }
private:
    Priority m_priority = High; // set init value to High
};

https://doc.qt.io/qt-5/properties.html

U7Development

Thanks for replies and welcome!

My apologies, i said properties because my fault, i use unreal engine, there i have properties the same as components..

What i want to do is to create a control, for instance a QPushButton from code, inside a class

[code]
class MyWindow : QMainWindow{
//some people used pointers
QPushButton * btn1 = nullptr;

  //but others standard variable
  QPushButton btn2;

};
[/ code]

Do both ways will serve for QT?

And thanks both for the explanation of Q_PROPERTY, that's new and welcome to learn 😁

mrjj

@U7Development
Hi
Ah. well its actually widgets then.
If you place the button as a member (in .h )
then syntax will work.
QPushButton btn2;

That said, if you have it as nonpointer and put it in a layout, you might get a double deletion
as both the layout and the class will try to delete it.

So while both syntaxes are fine, the
QPushButton * btn1 = new QPushButton;
are the most commonly used to avoid issues.

Do note Qt has a object system that will handle the deletion of Widgets so most of the time no
delete btn1 is needed if you insert into a parent. ( like a form)
explained here
https://doc.qt.io/qt-5/objecttrees.html

jsulm

@mrjj said in Very new to QT:

class MyWindow : QMainWindow{
QPushButton btn2; // this is local variable and will be deleted as soon as functions ends
};

It's a class not a function :-)

mrjj

@jsulm
omg yes, i saw it as the constructor :)
deleted. Thanks.