ittium<ittium@gmail.com> wrote in news:jd25dr$6b6$1@dont-email.me:
Group,
I have a small doubt regarding
http://www.parashift.com/c++-faq-lite/value-vs-ref-semantics.html#faq-3
1.4 As per this faq, only valid places(apart from virtual/dynamic
data) to use reference semantic are
- wrapper class
-N-to-1-uses-a relationship
These are generic terms, will appreciate if some one could explain or
probably direct me to some link. Google search did not offer much.
N-to-1 is easier to explain. This means that the same object of type A must
be accessible from N objects of type B. In C++, an object is a region of
memory, having a certain size (as reported by the sizeof() operator). As it
is physically impossible the some region of memory (A) belongs at the same
time into several different memory regions of same type (B), it means that
for having this kind of relationship, A must be a separate object and all B
objects should contain a pointer or reference to the A object.
With the wrapper classes it is not so clear what the author has meant. I
guess in this context this just means that the A object is already existing
and must remain accessible from other parts of the program as the A object.
Maybe it is a member in some std::map<A> or other container. However, other
parts of the program want to have access to the exact same object, but via
different interface. As it might not be possible or feasible to add this
interface directly to the A class, a wrapper class B is defined instead,
which provides the needed interface and forwards the actual function calls
to the original A object. For doing this it must contain a pointer or
reference to the A object.
"wrapper". Wrappers *usually* contain the object they "wrap".