Re: Are reference variables only good for function/method parameters?
Francis Glassborow wrote:
In article <1150752046.655804.263480@u72g2000cwu.googlegroups.com>,
kc_heaser@yahoo.com writes
I've read up and studied alot on what reference variables
are and what they do and even how they are implemented, but
I still don't feel like I have a complete understanding on
how they are used besides as parameters to methods and
functions.
Is this pretty much their sole reason for existence or are
there any other neat tricks or techniques that I'm unaware
of?
They are important as return types as well as for parameters.
This is particularly true for operators where excessive
passing and returning by value is not desirable.
Attention. Return by reference generally has significantly
different semantics than return by value, and the choice usually
depends on the semantics. Roughly speaking, operators which
result in an lvalue return references, and operators which don't
return values.
In addition references have the property of have both a static
(compile time or declarative) type and a dynamic (runtime)
type. This makes them important tools for runtime
polymorphism. A function may have a declared return type that
is a reference to a base class, but actually return a derived
type (object factories rely heavily on using either references
or pointers to dynamically created objects)
Note that this propogates further, and is often a reason to
declare a local variable as a reference, e.g.:
MyClass& c = someFunction() ;
In general, any time we don't want a copy, we need a reference
rather than a value. To make a copy, we need to know the
actual type at compile time, so this pretty much means that if
dynamic polymorphism is involved, we need references (or
pointers, of course). The same thing holds for entity objects
where identity is significant.
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