Rust Strings
Strings
Strings are used to store text, surrounded by double quotes.
You have already learned that you can use the &str type to create a string:
There are two main types of strings in Rust:
&str- is called "string slices", and is used for fixed text like"Hello"String- used when you need a string that can change
In this chapter, you will mostly work with the String type because it is more flexible and can be changed over time.
Create a String
You can create a String from a string literal using the to_string() method or the String::from()
function:
It is up to you which one to choose - both to_string() and String::from() are very common in Rust.
Change a String
Strings are mutable, so you can change them if they are declared with mut.
Use push_str() to add text to a string:
Example
let mut greeting = String::from("Hello");
greeting.push_str(" World");
println!("{}", greeting); // Hello World
Try it Yourself »
Use push() to add one character:
Example
let mut word = String::from("Hi");
word.push('!');
println!("{}", word); // Hi!
Try it Yourself »
Concatenate Strings
You can combine strings using the format! macro:
Example
let s1 = String::from("Hello");
let s2 = String::from("World!");
let s3
= String::from("What a beautiful day!");
let result = format!("{} {} {}",
s1, s2, s3);
println!("{}", result);
Try it Yourself »
You can also use the + operator to combine strings, but it can get messy with many values.
Example
let s1 = String::from("Hello");
let s2 = String::from("World!");
let s3 = String::from("What a beautiful
day!");
let result = s1 + " " + &s2 + " " + &s3;
println!("{}", result);
Try it Yourself »
Note: You can only add a &str to a String with +.
That is why &s2 and &s3 (a string slice) is used here.
Good to know: format! is often a better choice than using + for combining strings.
String Length
You can get the number of bytes in a string using the .len()
method:
