On Sun, Apr 6, 2014 at 7:50 PM, Philippe Delrieu
<philippe.delr...@free.fr> wrote:
> I need some more help.
>
> The impl Iterator<&mut ~Base> for Container declaration generate the error:
> error: missing lifetime specifier
> So I had it but I can't manage to return the next value with the specified
> life time.
> The code :
> impl<'a> Iterator<&'a mut ~Base> for Container {
> /// Advance the iterator and return the next value. Return `None` when
> the end is reached.
> fn next(&mut self) -> Option<&'a mut ~Base> {
> if self.iter_counter == self.nodeList.len() {
> None
> } else {
> self.iter_counter += 1;
> Some(&'a mut match **self.nodeList.get(self.iter_counter){
> FirstThinkImpl(first) => first as ~Base,
> SecondThinkImpl(second)=> second as ~Base,
> })
> }
> }
> }
>
> Generate these errors :
> test_enum.rs:58:18: 61:14 error: borrowed value does not live long enough
> test/test_enum.rs:58 Some(&'a mut match
Oh, I think I may have misleaded you... You cannot implement the
iterator directly in Container, because the iterator must handle the
current position, while the Container just holds the values. You need
a intermediate struct that implements the Iterator traits. That's what
the `iter()` and ' move_iter()` functions do for vectors and other
standard containers. So you'll need something along the lines of this
(disclaimer: totally untested!!):
struct Container {
//....
fn iter(&'a self) -> BaseItems<'a> {
let iter = nodeList.iter();
BaseItems{ iter : iter }
}
}
struct BaseItems<'a> {
iter : Items<'a, ~Base>
}
impl<'a> Iterator<&'a mut ~Base> for BaseItems<'a> {
//....
}
BTW, why all the double pointer in all the "&mut ~Base" instead of
just "&mut Base"?
--
Rodrigo
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