Initialization lists and passed parameters

[Josh Mcfarlane]

If the constructor for one of the objects within a class takes a
parameter of the constructor for the class and modifies it, when the
parameter is used in the constructor will it be the original parameter,
or the modified parameter after the initialization list?

Ex:

ClassA::ClassA(unsigned int& Parameter)
{
Parameter += 1;
}

ClassB::ClassB(unsigned int& ParameterB)
:ClassA(ParameterB)
{
Foo = Parameter;
}

In this case, if someone calls initializes the object as ClassB(0),
will Foo be 0 or 1?

Thanks,
Josh McFarlane

[Alipha]

Josh Mcfarlane wrote:

If the constructor for one of the objects within a class takes a
parameter of the constructor for the class and modifies it, when the
parameter is used in the constructor will it be the original parameter,
or the modified parameter after the initialization list?

Ex:

ClassA::ClassA(unsigned int& Parameter)
{
Parameter += 1;
}

ClassB::ClassB(unsigned int& ParameterB)
:ClassA(ParameterB)
{
Foo = Parameter;
}

In this case, if someone calls initializes the object as ClassB(0),
will Foo be 0 or 1?

Thanks,
Josh McFarlane

TRY IT. write a test case. run it. see for yourself.

[Victor Bazarov]

Josh Mcfarlane wrote:

If the constructor for one of the objects within a class takes a
parameter of the constructor for the class and modifies it, when the
parameter is used in the constructor will it be the original parameter,
or the modified parameter after the initialization list?

Ex:

ClassA::ClassA(unsigned int& Parameter)
{
Parameter += 1;
}

ClassB::ClassB(unsigned int& ParameterB)
:ClassA(ParameterB)
{
Foo = Parameter;
}

In this case, if someone calls initializes the object as ClassB(0),
will Foo be 0 or 1?

Foo should be 1. Why is there a doubt?

V

[Frank Chang]

Josh, Is there a reason why the constructors are not defined as
ClassA::ClassA(const unsigned int& Parameter)
{
//Parameter += 1; Parameter now const
}

ClassB::ClassB(const unsigned int& ParameterB)
:ClassA(ParameterB)
{
Foo = Parameter; // do you mean ParameterB?
}

Thank you.

[Old Wolf]

Victor Bazarov wrote:

Josh Mcfarlane wrote:

If the constructor for one of the objects within a class takes a
parameter of the constructor for the class and modifies it, when
the parameter is used in the constructor will it be the original
parameter, or the modified parameter after the initialization list?

Ex:

ClassA::ClassA(unsigned int& Parameter)
{
Parameter += 1;
}

ClassB::ClassB(unsigned int& ParameterB)
:ClassA(ParameterB)
{
Foo = Parameter;
}

In this case, if someone calls initializes the object as ClassB(0),
will Foo be 0 or 1?

Foo should be 1. Why is there a doubt?

There should be a compiler error (cannot bind a temporary to
a non-const reference).

[Josh Mcfarlane]

Frank Chang wrote:

Josh, Is there a reason why the constructors are not defined as
ClassA::ClassA(const unsigned int& Parameter)
{
//Parameter += 1; Parameter now const
}

ClassB::ClassB(const unsigned int& ParameterB)
:ClassA(ParameterB)
{
Foo = Parameter; // do you mean ParameterB?
}

Thank you.

Yes, I meant ParameterB. I may have dumbed down the example too much.
What I am doing is trying to recreate objects from a stream of data. In
the case of ClassB, it has to reconstruct ClassA first, and then classB
should begin it's construction from the new stream of data. I did this
by incrementing the buffer position (IE Buffer += SizeofBufferRead). I
just wanted to verify that ClassB would use the new Buffer start rather
than the original buffer start.

[Frank Chang]

Yes, I just verified that. On MSVC 7.1, the compiler error reads :

error C2664: 'ClassB::ClassB(unsigned int &)' : cannot convert
parameter 1 from 'int' to 'unsigned int &'

[Frank Chang]

Josh, Thank you for the explanation of your application. I tested your
code on MSVC7.1. The only problem I had was the compiler error OldWolf
discovered. But, that can be fixed once one read OldWolf's post.