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The Ultimate Guide to Rust Programming

Turbofish!

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Let’s go back to fruit. We can write static methods just as easily as normal methods. Behold, my new fruit!

Rust 1.40.0
struct Fruit<T> {
    apples: T,
    bananas: T,
}
impl Fruit<i32> {
    fn new() -> Self {
        Fruit {
            apples: 5,
            bananas: 10,
        }
    }
}
fn main() {
    let fruit = Fruit::new();
    assert_eq!(fruit.apples, 5);
    assert_eq!(fruit.bananas, 10);
    println!("Success!");
}

Pop quiz: what’s the type of the fruit variable in main? Given that we have an impl block for a Fruit<i32>, it seems a fair guess that the type is Fruit<i32>. And you’d be right. But how did Rust know you wanted that? Why not give you a Fruit<String>? That’s because there was only one static method on Fruit available, called ...