C++ - Behavior of enums in member object

Question

I am using Qt in C++ and am struggling with an enum. Consider a case like the one below: Clone on GitHub: https://github.com/jif/enum ``` // memberclass.h ======================================================= #ifndef MEMBERCLASS_H #define MEMBERCLASS_H #include class MemberClass : public QObject { Q_OBJECT public: enum ErrorType { NoError, IsError }; explicit MemberClass(QObject *parent = 0); void setError(ErrorType errorType); MemberClass::ErrorType error() const; void otherMethod(); private: MemberClass::ErrorType mError; }; #endif // MEMBERCLASS_H // memberclass.cpp ======================================================= #include "memberclass.h" #include MemberClass::MemberClass(QObject *parent) : QObject(parent) { mError = NoError; qDebug() << "mError initialized."; } MemberClass::ErrorType MemberClass::error() const { return mError; } void MemberClass::setError(ErrorType errorType) { mError = errorType; } void MemberClass::otherMethod() { qDebug() << " In oth…

Accepted Answer

You didn't define a default constructor for `MemberClass` and a compiler supplied implicit one is used to initialize `objectMember` in `ParentClass`. The implicit constructor does not initialize `mError` for you, thus the random value you get.

Either add a explicit default constructor to `MemberClass`:

```
MemberClass::MemberClass() :
    QObject(NULL), mError(NoError)
{
}
```

or a member initialization to `ParentClass`:

```
ParentClass::ParentClass(QObject *parent) :
    QObject(parent), objectMember(NULL)
{
    pointerMember = new MemberClass(this);
}
```

C++ - Behavior of enums in member object

Solution

Problem