Question

QObject *obj;
...
if ( /* obj is already instantiated */ ) {
    ;
} else {
    obj = new QObject();
}

My query is the condition of the if

Answer 1

1) Initialize your object pointer to NULL

2) Check for NULL in your if statement

QObject *obj = NULL;
...
if ( obj != NULL ) {
    ;
} else {
    obj = new QObject();
}