How to define a derived class in c++?

Question

I learnt Walter Savitch's Absolute C++ (5th ed.) about 2 years ago. The way to declare a derived class in this book is that

class ChildClass:Public ParentClass{...}

where the parent class is something like

class ParentClass
{Public:
 double getVariable() const;
...}

This book also says that if I do not want to change the definition of a member function of the parent class when I declare a derived class, I do not have to rewrite it in the derived class declaration. For example, if I do not want to change the definition of double ParentClass::getVariable() const, which assesses a member variable of ParentClass, I do not have to explicitly write it down again in the declaration of the derived class ChildClass.

Recently, I wanted to work out a project, and found something that changed over the years. Firstly, the declaration of the derived class should look like

class ChildClass:ParentClass{...}

You should not insert Public in front of ParentClass, otherwise, the compiler complains. Secondly, I cannot access the function double ParentClass::getVariable() const in the main program by the following code

childInstance.getVariable()

where childInstance is an instance of ChildClass.

These are the two things changing I found. Would you please tell me how to define a derived class in the correct way? Thank you!

By the way, the complier I am using is gcc 5.4.0 on Cygwin.

You probably should prefer one of [these books](https://stackoverflow.com/q/388242) and throw what you have into the bin. — user0042, Nov 26 '17 at 10:41
`Public` is something very different from `public`. One is wrong and the other is correct. — Some programmer dude, Nov 26 '17 at 10:43
And you should note that c++ is a case sensitive language. `Public` isn't the same as `public`. — user0042, Nov 26 '17 at 10:43

score 0 · Accepted Answer · answered Nov 26 '17 at 10:44

Public is nothing special in C++.

You should write public.

Even the syntax highlighting should tell you the error.

See this example:

if else for while public
Am Tree Hat House Public
                  ^~~~~~

After you've adapted to the correct keyword, there should be no more problems. By default things about class are private.

How to define a derived class in c++?

1 Answers1