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From: Daniel Krügler on 23 Jun 2010 21:49
On 23 Jun., 16:08, CoryG89 <cory...(a)gmail.com> wrote:
> Ok, so I am working on this for school. I am building a model
> business application in the console using C++.
>
> The application is modeled as a database/cashier program. I have a
> class called BookData that is supposed to hold a number of character
> arrays and a few other variables.

Since this is for your homework (and it's OK if
you say so), I can only give some hints such that
the educational value of your lessons don't get
lost.

> Here are my private members:
>
> char _isbn[14];
> char _title[51];
> char _author[31];
> char _publisher[31];
> char _date[11];
> int _quantity;
> double _cost;
> double _price;

Was this the pre-condition given by your teacher or
was this your own idea?

> I am supposed to have public accessor and mutator functions that 'get'
> and set' each private member of the class. I was surprised to learn
> this, but apparently you cannot return an array from a function in C++
>
> Normally I know I would write an accessor function for the last three
> similar to something like this:
>
> double BookData::getCost()
> {
> return _cost;
> }

In C++ an important concept is the notion of
const-correctness. You should be sure that
your members reflect this concept. How could
you improve above declaration?

> I am not sure how I should go about doing this for the character
> arrays. This is for a C++ course and I believe I am supposed to keep
> the c strings and not use strings from the standard libraries. I
> cannot remember but I think that you are supposed to use pointers to
> do this somehow. I tried but the syntax seems clumsy and I am getting
> errors. Any tips would be most appreciated.

It would be helpful, if you showed you attempts
to see where the actual problem is. Hint: In C and
C++ it often helps to invent a typedef to simplify
the complexity of a declaration.

> This is supposed to work by booting up and filling a dynamically
> allocated array of BookData class objects from a delimited data file.
> I need these 'setter' / 'getter' functions for accessing and
> manipulating these values to add other functionality. I am going to be
> working on this for the rest of tonight and all tomorrow. So anyone
> that can give me any advice on this subject would be most helpful.

As you observed, you cannot directly return
a built-in array by function. You have
different choices here: There is one choice,
which works via a "by-value" approach, but since
C arrays aren't completely self-descriptive,
you need a second parameter that provides
the missing information. Think about ways
of doing this. The alternative approach
is a "by-reference" approach, which would
return a reference to the member data. How
would you declare a typedef for a reference
to e.g. char[14]?

HTH & Greetings from Bremen,

Daniel Kr�gler



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From: red floyd on 24 Jun 2010 10:01
On Jun 24, 4:03 am, "Martin B." <0xCDCDC...(a)gmx.at> wrote:

> Leading underscores in names are reserved in C/C++
> Consider naming your members "m_isbn" or "isbn_" or maybe just "isbn".
>

Not quite. Leading underscores in names are reserved in the *global*
namespace in C++ (note that there is no such language as C/C++).

Since OP's _cost is a member variable, it's not in the global namespace,
and hence not reserved.

In addition, any identifier with a double underscore, or an leading
underscore followed by an *UPPER CASE* letter are reserved in all
contexts.


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