[ fromfile: children.xml id: qobjectchildmgmt ]

Example 8.2 shows a QObject derived class.^[65]

[ . . . . ]

class Person : public QObject {
 public:
    explicit Person(QString name, QObject* parent = 0);
    virtual ~Person();
};
[ . . . . ]

The complete implementation is shown in Example 8.3. Notice that ~Person() does no explicit object deletion. It simply displays the name of the object being destroyed (for teaching purposes).

#include "person.h"
#include <QTextStream>

static QTextStream cout(stdout);

Person::Person(QString name, QObject* parent)
         : QObject(parent) {
    setObjectName(name);
    cout << QString("Constructing Person: %1").arg(name) 
         << endl;
}

Person::~Person() {
    cout << QString("Destroying Person: %1").arg(objectName()) 
         << endl;
}

growBunch(), shown in Example 8.4, creates some objects, adds them to other objects, and then exits. All its local objects get destroyed when growBunch() returns.

[ . . . . ]
void growBunch() {
    qDebug() << "First we create a bunch of objects." << endl;
    QObject bunch;
    bunch.setObjectName("A Stack Object");  
    /* other objects are created on the heap */
    Person* mike = new Person("Mike", &bunch);
    Person* carol = new Person("Carol", &bunch);
    new Person("Greg", mike);               
    new Person("Peter", mike);
    new Person("Bobby", mike);
    new Person("Marcia", carol);
    new Person("Jan", carol);
    new Person("Cindy", carol);
    new Person("Alice");                    
    qDebug() << "\nDisplay the list using QObject::dumpObjectTree()"
             << endl;
    bunch.dumpObjectTree();                 
    cout << "\nReady to return from growBunch() -"
         << " Destroy all local stack objects." << endl;
}


int main(int , char**) {
   growBunch();
   cout << "We have now returned from growBunch()."
        <<  "\nWhat happened to Alice?" << endl;
   return 0;
}
[ . . . . ]

Following is the output of this program.

src/qobject> ./qobject
First we create a bunch of objects.
Constructing Person: Mike
Constructing Person: Carol
Constructing Person: Greg
Constructing Person: Peter
Constructing Person: Bobby
Constructing Person: Marcia
Constructing Person: Jan
Constructing Person: Cindy
Constructing Person: Alice

Display the list using QObject::dumpObjectTree()
QObject::A Stack Object
    QObject::Mike
        QObject::Greg
        QObject::Peter
        QObject::Bobby
    QObject::Carol
        QObject::Marcia
        QObject::Jan
        QObject::Cindy

Ready to return from growBunch() - Destroy all local stack objects.
Destroying Person: Mike
Destroying Person: Greg
Destroying Person: Peter
Destroying Person: Bobby
Destroying Person: Carol
Destroying Person: Marcia
Destroying Person: Jan
Destroying Person: Cindy
We have now returned from growBunch().
There is no way to access Alice.
src/qobject>