CODEWITHSUNDEEP
c++qtpolymorphismswapqobject
Jacob Krieg
Jacob Krieg

Reputation: 3184

Swap Qt Widgets

I am running into a problem. I want to swap two Qt widgets:

void swap(QMainWindow **w1, QMainWindow **w2)
{
    QMainWindow *w3;

    w3 = *w1;
    *w1 = *w2;
    *w2 = w3;
}

However if I have widget1 of type MainWindow1* and widget2 of type MainWindow2* and I call swap(&widget1, &widget2); I get

/home/user/Test/manager.cpp:24: error: invalid conversion from 'MainWindow1**' to 'QMainWindow**' [-fpermissive]
  swap(&widget1, &widget2);
       ^

I must note that MainWindow1 and MainWindow2 are two QMainWindow derived classes.

My question is: Is it possible to create a function that swaps at runtime two polymorphic objects? How can I get around this issue?

Thanks a lot!

Upvotes: 1

Views: 1338

Answers (1)

Lahiru Chandima
Lahiru Chandima

Reputation: 24138

You should not be passing MainWindow1 and MainWindow2 pointers to swap like below.

MainWindow1* w1 = new MainWindow1();
MainWindow2* w2 = new MainWindow2();
swap(&w1, &w2);

If swap could happen in this case, MainWindow1 pointer would point to a MainWindow2 object, which is not right.

You have to pass MainWindow pointers to swap like below.

MainWindow* w1 = new MainWindow1();
MainWindow* w2 = new MainWindow2();
swap(&w1, &w2);

Upvotes: 2

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