Re: Nonstatic member example?
On Dec 31, 1:12 pm, "Jim Langston" <tazmas...@rocketmail.com> wrote:
James Kanze wrote:
On Dec 31, 5:45 am, "Jim Langston" <tazmas...@rocketmail.com> wrote:
fl wrote:
[...]
class Bar {
public:
Bar( Bar& foo ): d( foo ) {}
private:
Bar& d;
};
Note that if that's the only constructor, there's no way to
create an instance of the class, because in order to create an
instance, you have to have an instance. (Note too that your
constructor is a copy constructor. I'm not sure if this is
intentional or not---it doesn't have the classical copy
semantics, but on the other hand, I can't imagine any other
reasonable approach if you don't want to have to test for null
pointers, etc.)
About the only case I can imagine where a reference to the class
itself would make sense if if you provide a default constructor
which initializes it to *this. Given the usual way people
understand things, I rather suspect that in such cases, most of
the time, using pointers would result in more understandable
code. But that may just be me.
Yes, you are right. Although this compiles:
class Foo
{
public:
Foo( Foo& foo ): Ref( foo ) {}
Foo(): Ref( *this ) {}
private:
Foo& Ref;
Foo& operator=( Foo& foo ) {}
};
main()
{
Foo foo;
Foo bar( foo );
}
As it should. (And BTW: you don't need the private operator=,
since the compiler won't generate one if the class contains a
reference member.)
I could think of someone attempting to do something like this
for a linked list with the first declaration being the head,
but I think the destructer would cause problems as you can't
reseat a reference. It could be done, but probably shouldn't.
It can't be used for a dynamic structure, that's for sure. On
the other hand, I can imagine it being used for a static tree,
although even then... Maybe it's just me, but when I'm
navigating through a tree, it feels strange to use references,
and not pointers, even if the tree is actually constructed by
the compiler, and you never need to reseat the references.
Also, of course, I'd generally prefer a nul pointer when there
is no corresponding entry (e.g. the parent of the root), rather
than a reference to the object itself.
--
James Kanze (GABI Software) email:james.kanze@gmail.com
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