# V1106. Qt. Class inherited from 'QObject' should contain at least one constructor that takes a pointer to 'QObject'.

The analyzer has detected a class inherited from 'QObject' that does not contain any constructors that take a pointer to 'QObject' as a parameter.

Objects inherited from the 'QObject' type are organized in trees with parent-child relations. When another object is created, a pointer to the parent object is passed. In a parent object, the inherited object is added to the list of children. This ensures that when the parent object is deleted, all of its child objects are also deleted.

So, when writing your classes based on the Qt library, add an overload that takes a pointer to 'QObject' — that's a good coding practice. The analyzer issues a warning if it does not find a constructor that takes such a pointer.

Let's look at an example:

    class MyCounter : public QObject
    {
      Q_OBJECT;
    public:
      MyCounter (int startValue);
    };

The 'MyCounter' class has no constructors that take pointers to 'QObject'. The fixed code may look like this:

    class MyCounter : public QObject
    {
      Q_OBJECT;
    public:
      MyCounter (int startValue, QObject *parent = nullptr); // ok
    };

Note. Due to peculiarities of some projects, the analyzer does not issue the warning if it detects at least one constructor that takes a pointer to a parent object.

This diagnostic is classified as:

CWE-772