How to convert Vec to a string

Use collect() on an iterator:

let v = vec!['a', 'b', 'c', 'd'];
let s: String = v.into_iter().collect();
println!("{}", s);

The original vector will be consumed. If you need to keep it, use v.iter():

let s: String = v.iter().collect();

There is no more direct way because char is a 32-bit Unicode scalar value, and strings in Rust are sequences of bytes (u8) representing text in UTF-8 encoding. They do not map directly to sequences of chars.