Class Identifier used inside the class declaration. Is it a good practice?

Question

While reviewing one of our C++ class through coverity, it showed an error message on a particular class. The class is as follows:

class InputRecord
{
    /* Construtor */
    ...
    InputRecord::RejectRecord();
    ...
    /* Destructor */
}

What is the significance of using an identifier inside the class? Is it a good practice to follow this?

Thanks, Mathew Liju

Answer 1

G'day,

I always thought that sort of identifier was only used in the implementation and wasn't necessary in the class definition.

A class declaration is

class InputRecord;

What you've got there is a class definition.

class InputRecord
{
    /* Construtor */
    ...
    RejectRecord();
    ...
    /* Destructor */
}

then in your .cpp file you have the implementation

InputRecord::RejectRecord()
{
    ...
}

Answer 2

In general, there aren't any cases where the disambiguation provided by the explicit InputRecord:: in your code sample are likely to be anything other than redundant.

If the code is doing complex manipulations where the specific class is relevant (say you're passing it to a base class that has a shadowed version), then it may help code clarity to make it explicit.

It's a bit like using this-> (or this. in C#/Java).

Personally I'd remove any such redundant specifiers and find another way of getting the point across.

Answer 3

On gcc compilers (v4.1 and above) this would fail to compile with "error: extra qualification". It's therefore good practice not to put it there!

See here which discusses the extra qualification as not legal C++.

Answer 4

In the class definition, I only use class identifiers if I have parameters that are named similarly (or the same) to private members of the class. It avoids ambiguity and also makes the code easier to read at the same time. I can't think of another case in which you would need to use it.