Avoid default constructor for member variable

Question

I have a class with a member variable of another class:

class MeasurementUnit {
private:
    MeasurementMultiplier _multiplier;

Actually I would not need a default constructor for MeasurementMultiplier, because actually I will initialize with parameters MeasurementMultiplier(a,b,c), and I would - but can't directly:

C2864: 'MeasurementUnit::_multiplier' :
only static const integral data members can be initialized within a class

So I need the default constructor, without it does not compile error: C2512: 'MeasurementUnit' : no appropriate default constructor available

Can I avoid needing the default constructor?

Use an initializer list or get a compiler that supports C++11 in-class member initialization. — chris, Mar 14 '13 at 21:31
http://www.learncpp.com/cpp-tutorial/101-constructor-initialization-lists/ — David Heffernan, Mar 14 '13 at 21:31
You may need to reword this question? I for one didn't understand it. — Edward Strange, Mar 14 '13 at 21:31
You could give default parameter values to some other constructor. — QuentinUK, Mar 14 '13 at 21:33

Daniel Frey · Accepted Answer · 2013-03-15T09:56:05.050

6

In all constructors of your class MeasurementUnit, you need to initialize the member variable _multiplier in the initializer list. Example:

MeasurementUnit::MeasurementUnit()
  : _multiplier(1,2,3)
{}

edited Mar 15 '13 at 09:56

answered Mar 14 '13 at 21:31

Daniel Frey

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Sorry,I do not get it. By doing so you have a default constructor,this is what I want to avoid. – Horst Walter Mar 14 '13 at 21:45
1

@HorstWalter: In this case I don't get your question. The *example* I gave refers to the (default) constructor of `MeasurementUnit` to avoid the need for a default constructor of `MeasurementMultiplier`. If this is not what you wanted, please edit and clarify the question. – Daniel Frey Mar 14 '13 at 21:49
1

@HorstWalter: And I just realized *my* mistake of mixing up the member variable's name and its type. I edited the answer accordingly, sorry for the confusion it might have caused. – Daniel Frey Mar 15 '13 at 09:58

score 1 · Answer 2 · edited May 23 '17 at 10:25

1

Use MIL - Member Initialization List MIL

edited May 23 '17 at 10:25

Community

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answered Mar 14 '13 at 21:33

user1708860

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Avoid default constructor for member variable

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