Rustlings solution | lifetimes

// lifetimes1.rs
//
// The Rust compiler needs to know how to check whether supplied references are
// valid, so that it can let the programmer know if a reference is at risk
// of going out of scope before it is used. Remember, references are borrows
// and do not own their own data. What if their owner goes out of scope?
//
// Execute `rustlings hint lifetimes1` or use the `hint` watch subcommand for a hint.

fn longest<'a>(x: &'a str, y: &'a str) -> &'a str {
    if x.len() > y.len() {
        x
    } else {
        y
    }
}

fn main() {
    let string1 = String::from("abcd");
    let string2 = "xyz";

    let result = longest(string1.as_str(), string2);
    println!("The longest string is '{}'", result);
}

// lifetimes2.rs
//
// So if the compiler is just validating the references passed
// to the annotated parameters and the return type, what do
// we need to change?
//
// Execute `rustlings hint lifetimes2` or use the `hint` watch subcommand for a hint.

fn longest<'a>(x: &'a str, y: &'a str) -> &'a str {
    if x.len() > y.len() {
        x
    } else {
        y
    }
}

fn main() {
    let string1 = String::from("long string is long");
    let result;

    let string2 = String::from("xyz");
    result = longest(string1.as_str(), string2.as_str());

    println!("The longest string is '{}'", result);
}

// lifetimes3.rs
//
// Lifetimes are also needed when structs hold references.
//
// Execute `rustlings hint lifetimes3` or use the `hint` watch subcommand for a hint.

struct Book<'a> {
    author: &'a str,
    title: &'a str,
}

fn main() {
    let name = String::from("Jill Smith");
    let title = String::from("Fish Flying");
    let book = Book {
        author: &name,
        title: &title,
    };

    println!("{} by {}", book.title, book.author);
}