Mastering Rust - Second Edition

Using strings in functions

It's idiomatic and performant to pass string slices to functions. Here's an example:

// string_slices_func.rsfn say_hello(to_whom: &str) {     println!("Hey {}!", to_whom) } fn main() {     let string_slice: &'static str = "you";     let string: String = string_slice.into();     say_hello(string_slice);     say_hello(&string); } 

To the astute observer, the say_hello method also worked with a &String type. Internally, &String automatically coerces to &str, due to the type coercion trait Deref implemented for &String to &str. This is because String implements Deref for the str type.

Here, you can see why I stressed the point earlier. A string slice is an acceptable input parameter not only for actual string slice references ...