The trait `FnMut<(char,)>` is not implemented for `String` when trying to split a string

Question

I need to split a String (not &str) by another String:

use std::str::Split;

fn main() {
    let x = \"\".to_strin         


        

Answer 1

I talked about this with #rust-beginners IRC channel and heard the following:

15:12:15           achird | d33tah: split accepts a Pattern, where Pattern can be &str or char, but you're passing a String (no idea why deref is not working)
15:13:01           d33tah | achird: thanks! how can I convert string to str?
15:13:03           achird | i think a simple split(&delimiter2) should fix the problem
15:16:26           calops | why isn't deref working though?
15:21:33        @mbrubeck | calops, d33tah: Deref coercions only work if one exact "expected" type is known.  For a generic type like <P: Pattern>, coercion doesn't kick in.
15:24:11        @mbrubeck | d33tah: The error should definitely be improved...  It should complain that `String` doesn't impl `Pattern`, instead of jumping straight to `FnMut(char)`

So basically, the solution is to add & before the delimiter string, like this:

fn main() {
    let s1 = "".to_string();
    let s2 = "".to_string();
    let x = s1.split(&s2);
}

Answer 2

All is in the documentation. You can provide one of:

• A &str,
• A char,
• A closure,

Those three types implement the Pattern trait. You are giving a String to split instead of a &str.

Example:

fn main() {
    let x = "".to_string();
    let split = x.split("");
}