How do I find the index of an element in an array, vector or slice?
TLDR Use an iterator with the position
method, the Rust docs shows a good example.
No, it's because indices are usize
, not i32
. In fact, i32
is completely inappropriate for this purpose; it may not be large enough, and there's no reason for it to be signed. Just use usize
.
Some other notes: calling to_string()
is not free, and you don't need it for the comparison; you can compare string slices just fine!
Also, if you really want to turn a usize
into an i32
, you can do that with a cast: x as i32
, though this will not produce an error on over- or under-flow (i.e. the result may be negative).
All that said, as noted in Mathieu David's answer, there's a position
method on iterators that does what you want.
I think you should look at the position
method instead.
fn main() {
let test = vec!["one", "two", "three"];
let index = test.iter().position(|&r| r == "two").unwrap();
println!("{}", index);
}
You can test it here.
Note that this works for any iterator, so it can be used for vectors, arrays, and slices, all of which produce iterators.