Understanding String vs &str in Rust

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Understanding String vs &str in Rust

Rust has two main string types: owned String and borrowed string slices (&str). String is heap-allocated and growable, while &str is a reference to string data (either borrowed or stored in the binary). Functions accepting &str are more flexible since they work with both types.

snippet.rs
rust
fn print_greeting(message: &str) {
    println!("Hello, {}!", message);
}
 
fn main() {
    let owned = String::from("World");
    print_greeting(&owned);
    
    let literal = "Rustacean";
    print_greeting(literal);
}

Breakdown

fn print_greeting(message: &str)

Function that accepts any string-like reference, very flexible

let owned = String::from("World");

Creates a heap-allocated String, owns the data

print_greeting(&owned);

Passes a reference to the owned String

let literal = "Rustacean";

String literal stored in the program binary

print_greeting(literal);

Passes the string slice directly

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Understanding String vs &str in Rust

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