String and str

Difference between String and str

String is similar to Vec<T>. It is similar to the C++ String class.

str is similar to char[]. Just as C++ uses a variable name as a pointer when working with a char array, Rust usually uses str through a reference by putting & in front of it.

Type conversion

How do you convert a String into &str?

Put &* in front of the String. See Deref.

let s = String::from("hello world")
let ss = *s; //str type, Deref coerce
let sss = &*s; //&str

Or use the as_str() function.

let s = String::from("hello world")
let ss = s.as_str; //&str

How do you convert &'static str into String?

Use to_string().

Converting &str into String requires allocation, so avoid it when possible.

let s = "hello world";
let ss = s.to_string();

Byte String Literal

b"whatever" is a byte string literal. Its type is buf: &[u8; 8].

let s = b"hello world"; //buf:&[u8;11]
let ss =  b"whatever"; //buf:&[u8;8]