C++ Inheritance Question

[tatteredpotato]

Most of my programming experience insofar has been C# and Java, I've been working with C++ lately and my question is about the use of the public modifier when using inheritance.

An Example:

class BaseClass
{
// Blah Blah Blah
};

class DerivedClass : public BaseClass
{
// More Blah
}

What is the meaning of the "public" following the colon? I've been looking around on the internet and most things just say to use it without commenting on its meaning.

Also, would:

class DerivedClass : private BaseClass {};

or

class DerivedClass : BaseClass{};

ever desirable?

 

[Markbnj]

Here's a good discussion:

http://publib.boulder.ibm.com/...nguage/ref/cplr130.htm

Inheriting privately is really composition, not specialization. I don't care for it, and didn't use it once (as far as I can recall) in 10 years of C++ development.

 

[tatteredpotato]

I see, so essentially using private would essentially encapsulate your base class within your derived class, meaning you wouldn't have access to any public members of BaseClass outside of the derived class (unless you write that functionality back into your derived class).

 

[EagleKeeper]

Originally posted by: ObscureCaucasian
I see, so essentially using private would essentially encapsulate your base class within your derived class, meaning you wouldn't have access to any public members of BaseClass outside of the derived class (unless you write that functionality back into your derived class).

Correct

Private blocks people from outside the class from sneaking a peek as to what is inside.

Private is the default; so you must declare Public what you desire to expose.

 

[Markbnj]

And the main point is, that having blocked public visibility of those inherited members, the derived type cannot be said to have an "is-a" relationship with the base type. Thus my calling it composition rather than specialization. There are better and more explicit means of creating composition relationships, so I stay away from private inheritance.