Re: How to make iterating through list of variables more elegant

From:
Victor Bazarov <v.bazarov@comcast.invalid>
Newsgroups:
comp.lang.c++
Date:
Mon, 12 Jul 2010 13:23:55 -0400
Message-ID:
<i1fj3c$mgh$1@news.eternal-september.org>
On 7/12/2010 12:56 PM, Angus wrote:

I have the following string variables in my class:

m_PrimaryID, m_SecondaryID and m_TertiaryID.


Apparently, those are pointers to char or something convertible to a
pointer to char... It would be nice if you spelled it out for us,
instead of making us deduce this. Like so:

    class CTool // or does it inherit from something?
    {
       char* m_PrimaryID;
       char* m_SecondaryID;
       char* m_TertiaryID;
       // other stuff irrelevant
    public:
       const char* getID(int) const;
       CTool* findTool(const char*); // or is it inherited?
       CTool* FindTool();
       bool Exists();
       // other interface not important
    };

I have a search function, FindTool(), which goes through each of these
ID's to search for something.

I have a getID() function like this:
const char* CTool::getID(int index) const
{
     switch(index)
     {
       case 0: return m_PrimaryID&& *m_PrimaryID ? m_PrimaryID : 0;
       case 1: return m_SecondaryID&& *m_SecondaryID ?
m_SecondaryID : 0;
       case 2: return m_TertiaryID&& *m_TertiaryID ? m_TertiaryID :
0;
       default: return 0;
     }
}

which returns the requisite variable if not null.

I do the search like this:
CTool* CTool::FindTool()
{
     CTool* tool = 0;
     //try all available gcid's
     for(int it = 0; it != 3; ++it)
     {
        if(getID(it))
           tool = findTool(getID(it)); //this is using library I need
to use


"Need" as in "must"? Or "need" as in "has the functionality I don't
want to reinvent"? Is that a member of the base class? Is that a
global function? Consider supplying 'this->' in the former case and the
namespace prefix '::' in the latter.

You can declare a local variable instead of calling 'getID' twice:

   if (const char *cid = getID(it))
      tool = findTool(cid);

Is that more elegant? I think so.

        if(tool&& tool->Exists())
           return tool;
      }

    return 0;
}

But I am concerned the code looks obscure. How can I make it more
elegant?


Naming functions better might help (you have both 'getID' and
'FindTool', which are mixing different case conventions - bad). Adding
comments would certainly make the code more readable (and thus less
obscure)... Prefixes to the function to avoid misinterpreting global
functions as members (when read by a human, apparently the compiler has
no problem). Better control of the whitespace and indentation would help...

Anyway, what's your definition of "elegant"? Is that "I know one when I
see it"?

V
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