expected struct `String` found struct `Vec<&String>` - rust

Question

I have a function to reverse characters in words and I need to know how to convert a Vec<&String> into a regular owned String (with spaces between the words).
fn reverse_words(words: &str) -> String {
let mut split = words.split_whitespace();
let vec: Vec<&str> = split.collect();
let vec2 = vec!();
for word in vec {
vec2.push(&word.chars().rev().collect::<String>());
}
return vec2;
}
.
error[E0308]: mismatched types
--> src/lib.rs:8:12
|
1 | fn reverse_words(words: &str) -> String {
| ------ expected `String` because of return type
...
8 | return vec2;
| ^^^^ expected struct `String`, found struct `Vec`
|
= note: expected struct `String`
found struct `Vec<&String>`
For more information about this error, try `rustc --explain E0308`.
error: could not compile `challenge` due to previous error
NOTE: Line numbers in error messages can be incorrect due to concatenation.

Answer 1

Here is a version of your code with minimal changes to make it work. You basically only need to add a .join(' ') to your last statement:
fn reverse_words(words: &str) -> String {
let split = words.split_whitespace();
let vec: Vec<&str> = split.collect();
let mut vec2 = vec![];
for word in vec {
vec2.push(word.chars().rev().collect::<String>());
}
vec2.join(" ")
}
fn main() {
let sentence = "hello world";
assert_eq!(reverse_words(sentence), "olleh dlrow");
}
Playground.
This is an inefficient implementation requiring a lot of allocation though. You can chain methods of the Iterator trait to get a solution that does not require as much allocation:
fn reverse_words(words: &str) -> String {
words
.split_whitespace()
.map(|w| w.chars().rev().chain([' ']))
.flatten()
.take(words.len())
.collect::<String>()
}
fn main() {
let sentence = "hello world";
assert_eq!(reverse_words(sentence), "olleh dlrow");
}
Playground.