I'm trying to build an iterator over the rows of a table, and I'm using a lib that reads this. That lib had a proper iterator. I want to know how to chain these two iterators, I mean, when I call next on my iterator the next of the lib calls too.
impl Iterator for MyStruct {
type Item = item;
fn next(&mut self) -> Option<Self::Item> {
records().next()
}
}
I did that, but this calls only the first next every time, I want all the rows of the lib iterator.
By calling records() inside of the next() function, you are creating a new iterator every time, so you start from the beginning at every next() call.
You need to store the records iterator in the struct and then re-use it instead of re-creating it every time. That way it keeps its state between calls.
Look at this example:
fn records() -> impl Iterator<Item = i32> {
(1..5).into_iter()
}
struct MyStruct {
records_iter: Box<dyn Iterator<Item = i32>>,
}
impl MyStruct {
fn new() -> Self {
Self {
records_iter: Box::new(records()),
}
}
}
impl Iterator for MyStruct {
type Item = i32;
fn next(&mut self) -> Option<Self::Item> {
self.records_iter.next()
}
}
fn main() {
let my_obj = MyStruct::new();
for element in my_obj {
println!("{}", element);
}
}
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