Understanding String and &str

Snippet

Understanding String and &str

Rust has two main string types: String for owned, growable strings and &str for borrowed string slices. String::from creates an owned string from a string literal. Using &str is more efficient when you don't need ownership.

snippet.rs
rust
fn main() {
    let greeting = String::from("Hello");
    let slice = &greeting[..4];
    
    println!("Full: {}", greeting);
    println!("Slice: {}", slice);
    
    let s1 = "literal string";
    let s2: &str = s1;
    
    println!("s1: {}, s2: {}", s1, s2);
}

Breakdown

let greeting = String::from("Hello");

Creates an owned String type, heap-allocated and mutable

let slice = &greeting[..4];

Creates a borrowed &str slice from the String, borrowing first 4 characters

let s1 = "literal string";

String literals are &str by default, stored in binary

let s2: &str = s1;

Slices can be assigned without copying, just borrowing

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Understanding String and &str

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