Is it good practice to make member variables protected? [closed]

Answer 1

Your overall class design will show you if you will end up with protected members or not. Whether you make them private, protected or public, that isn't something thats chiseled in the stone, so feel free to create your class tree without much thinking about that. If at first you don't know if the member will be used by derived class, and in what way, you'll surely find out when coding.

Most important thing to decide is what is public vs /private, because that's the way you present your class to the outside world.

Answer 2

If you think child classes will need access to those variables later then yes, make them protected.

There is no drawback, as long as the aforementioned condition is met.

If you want to take the extra step and protect your variables from outside access, you could always create private member variables and then use protected methods to access/modify those private variables.

Answer 3

I am curious of what other people will answer to that.

As well as for the accessors paradigm, you may declare them private and use protected Getter and Setter methods. If your base class implementation changes, you only have those getter and setter to modify.

Answer 4

Personnally, I usually try to restrict my use of protected to virtual things.

I consider any other use of protected as conceptually equivalent to public. In the sense that if you write a non virtual protected method, write it as if it was public. Same for a field. If the field would break something if it was public, it will also break something if it's protected.

It doesn't mean it's bad to have a protected field or non virtual method, it just means you have to be careful and deliberate with their use, and know that someone, somewhere, can use those things and potentially break your class simply by deriving it.

Answer 5

Provide a protected getter and maybe setter to the private internal variable, it's a little more code, but it's much cleaner.

Answer 6

Inheriting is just another way of using a class. It is more coupled and by making your member variables protected, you couple even more, so you shouldn't change them without knowing the impact on every inherited class. If it is your base-class and your inherited classes, there's probably not going to be any harm, but you do lose control of how members should be accessed (locking, logging, read/write, persistency,...).