How do I find the index of an element in an array, vector or slice?

Question

I need to find an index of an element in a vector of strings. This is what I got so far:

fn main() {     let test: Vec<String> = vec![         "one".to_string(),         "two".to_string(),         "three".to_string(),         "four".to_string(),     ];      let index: i32 = test         .iter()         .enumerate()         .find(|&r| r.1.to_string() == "two".to_string())         .unwrap()         .0; } 

It produces an error:

error[E0308]: mismatched types   --> src/main.rs:9:22    | 9  |       let index: i32 = test    |  ______________________^ 10 | |         .iter() 11 | |         .enumerate() 12 | |         .find(|&r| r.1.to_string() == "two".to_string()) 13 | |         .unwrap() 14 | |         .0;    | |__________^ expected i32, found usize 

I assume that's because enumerate() returns a tuple of (usize, _) (correct me if I'm wrong), but how do I convert usize to i32 here? If there is a better approach, I'm open to suggestions.

Answer 1

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.