Initialize member in class constructor and pass member down to base class at the same time

Question

I have a main class (MyClass) derived from MyBase. Also I have a Helper class (used by MyClass) derived from HelperBase (used by MyBase). Is there a way to initialize the Helper in the constructor initialization of MyClass and also pass the helper down to MyBase that takes a HelperBase as constructor argument? Something as follows:

EDIT: forgot to derive Helper from HelperBase (as mentioned in the comments) fixed that in the sample code

//-------------------------------------------
// HelperBase.h
class MyBase;

// HelperBase holds a ref to MyBase
class HelperBase {
public:
    HelperBase(MyBase& i_ParentBase);

protected:
    MyBase& m_ParentBase;
};
// HelperBase.cpp
HelperBase::HelperBase(MyBase& i_ParentBase)
    : m_ParentBase(i_ParentBase)
{}
//-------------------------------------------
// Helper.h
class MyClass;

// Helper holds a ref to MyClass
class Helper : public HelperBase{
public:
    Helper(MyClass& i_Parent);

protected:
    MyClass& m_Parent;
};
//-------------------------------------------
// MyBase.h
// MyBase holds a ref to HelperBase
class MyBase {
public:
    MyBase(HelperBase& i_HelperBase);

protected:
    HelperBase& m_HelperBase;
};
// MyBase.cpp
MyBase::MyBase(HelperBase& i_HelperBase) : m_HelperBase(i_HelperBase)
{}
//-------------------------------------------
// MyClass.h
// MyClass holds and initializes an instance of Helper
class MyClass : public MyBase
{
public:
    MyClass();

protected:
    Helper m_Helper;
};
// MyClass.cpp
MyClass::MyClass()
    : MyBase(m_Helper), // <-- this is the problem !!!
    m_Helper(*this)
{}
//-------------------------------------------
// Helper.cpp
Helper::Helper(MyClass& i_Parent)
    : HelperBase(i_Parent),
      m_Parent(i_Parent)
{}
//-------------------------------------------

Did you forget to derive `Helper` from `HelperBase`? Then, in `Helper` constructor, you'll need `: HelperBase(i_Parent)`, and the constructor itself needs to be moved down below the definition of `MyClass`. — HolyBlackCat, Nov 05 '21 at 17:14
@HolyBlackCat, obviously you're absolutely right. I fixed that now. — Robin Holenweger, Nov 08 '21 at 08:19

score 0 · Answer 1 · answered Nov 09 '21 at 14:19

0

In the end it turned out the code works as above. There was a hidden/not so obvious naming convention clash that made the thing not compiling as expected (and the compile error did not reveal that at first sight). Sorry for that.

answered Nov 09 '21 at 14:19

Robin Holenweger

321
3
14

Initialize member in class constructor and pass member down to base class at the same time

1 Answers1