String Basics: String vs &str

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String Basics: String vs &str

Rust has two main string types: String (owned, heap-allocated) and &str (borrowed string slice). String is growable and mutable, while &str is a read-only view into text. Use String when you need ownership and &str when you only need to read or borrow text.

snippet.rs
rust
fn main() {
    // Creating a String from a string literal
    let greeting: String = String::from("Hello");
    
    // Creating a string slice reference
    let slice: &str = "World";
    
    // Pushing a string slice to a String
    let mut combined = greeting;
    combined.push_str(" ");
    combined.push_str(slice);
    
    // Getting the length
    println!("Length: {}", combined.len());
    
    // Checking if empty
    println!("Is empty: {}", combined.is_empty());
    
    // Converting String to &str (borrowing)
    let as_str: &str = &combined;
    println!("As &str: {}", as_str);
}

Breakdown

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

Creates an owned String from a string literal using the from constructor

let slice: &str = "World";

Creates a string slice reference pointing to static string data

combined.push_str(slice);

Appends a string slice to the String without taking ownership of slice

combined.len()

Returns the byte length of the string (not character count for UTF-8)

let as_str: &str = &combined;

Creates a borrowed reference to the String, converting &String to &str

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String Basics: String vs &str

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