Rust by Example

34 Strings

There are two types of strings in Rust: String and &str.

A String is stored as a vector of bytes (Vec<u8>), but guaranteed to always be a valid UTF-8 sequence. String is heap allocated, growable and not null terminated.

&str is a slice (&[u8]) that always points to a valid UTF-8 sequence, and can be used to view into a String, just like &[T] is a view into Vec<T>.

#![feature(collections)] #![feature(core)] #![feature(str_words)] fn main() { // (all the type annotations are superfluous) // A reference to a string allocated in read only memory let pangram: &'static str = "the quick brown fox jumps over the lazy dog"; println!("Pangram: {}", pangram); // Iterate over words in reverse, no new string is allocated println!("Words in reverse"); for word in pangram.words().rev() { println!("> {}", word); } // Copy chars into a vector, sort and remove duplicates let mut chars: Vec<char> = pangram.chars().collect(); chars.sort(); chars.dedup(); // Create an empty and growable `String` let mut string = String::new(); for c in chars { // Insert a char at the end of string string.push(c); // Insert a string at the end of string string.push_str(", "); } // The trimmed string is a slice to the original string, hence no new // allocation is performed let chars_to_trim: &[char] = &[' ', ',']; let trimmed_str: &str = string.as_slice().trim_matches(chars_to_trim); println!("Used characters: {}", trimmed_str); // Heap allocate a string let alice = String::from_str("I like dogs"); // Allocate new memory and store the modified string there let bob: String = alice.replace("dog", "cat"); println!("Alice says: {}", alice); println!("Bob says: {}", bob); }

More str/String methods can be found under the std::str and std::string modules