Re: hasMember

From:

Andrea Crotti <andrea.crotti.0@gmail.com>

Newsgroups:

comp.lang.c++

Date:

Thu, 09 Dec 2010 01:51:55 +0100

Message-ID:

<m11v5rrcno.fsf@ip1-201.halifax.rwth-aachen.de>

Jeff Flinn <TriumphSprint2000@hotmail.com> writes:

To avoid the memory allocation and ownership issues use boost::optional.

  #include <boost/optional.hpp>

  typedef boost::optional<int> optional_int;

  optional_int Cont::getValue(int idx) const
  {
     std::map<int, int>::const_iterator itr = content.find(idx);

     return (itr != cont.end())? itr->second : optional_int();
  }

and:

  if(optional_int i = obj.getValue(idx)) // safe bool idiom
  {
     int x = *i + 123; // deref for value
  }

Using exceptions in this case could be good?

Seems out of place for the use you've described, given what little
info you've provided.

Jeff

Interesting the optional_int, but I can't use boost...
Anyway I didn't specify much because is a general (for me) problem,
every time I have a class which has some structure (set/vector/map) I
might want to check and get some values from it.

So returning -1 or NULL is for me not nice, using exceptions I meant
something like done in std::vector::at for example

try {
int x = vec.at(0);
} catch ...

I could throw an exception whenever I don't find the value and catch it
in the caller, that's what I meant..