Iterators...

[Vij]

How can I check if an iterator is still valid and can be still
dereferenced ?

 

[Alan Johnson]

How can I check if an iterator is still valid and can be still
dereferenced ?

There is no (portable) way.

If you need to hand out handles to an object that might suddenly
disappear, you need to add an extra level of indirection. That is,
create a reference counted object that won't disappear until all the
references to it are gone, and have that object contain a pointer to the
real object.

For a well designed and widely tested implementation of such an idea,
see boost::shared_ptr and boost::weak_ptr.
<url: http://boost.org/libs/smart_ptr/smart_ptr.htm>

 

[Vij]

What is the non protable way to test this. (if there indeed is any way
?)

 

[Alan Johnson]

What is the non protable way to test this. (if there indeed is any way
?)

Sorry, I just added that because without it someone would almost
certainly come along saying, "But, on platform X you can do Y!" The
truth is that in most implementations I've seen there isn't any way at all.

 

[benben]

How can I check if an iterator is still valid and can be still
dereferenced ?

By analyzing the code you write. Usually, if you are not so aware of the
validity of a particular iterator, abandon it and ask for a valid one.
This is because iterators are more like handle to a position in a
container instead of an object.

Ben