Enlaces - Rust By Example
Description: Rust by Example (RBE) is a collection of runnable examples that illustrate various Rust concepts and standard libraries.

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# Enlaces

Indirectly accessing a variable makes it impossible to branch and use that variable without re-binding. `match` provides the `@` sigil for binding values to names:

    // A function `age` which returns a `u32`.
    fn age() -> u32 {
        15
    }

    fn main() {
        println!("Tell me what type of person you are");

        match age() {
            0             => println!("I haven't celebrated my first birthday yet"),
            // Could `match` 1 ..= 12 directly but then what age
            // would the child be?
            // Could `match` n and use an `if` guard, but would
            // not contribute to exhaustiveness checks.
            // (Although in this case that would not matter since
            // a "catch-all" pattern is present at the bottom)
            // Instead, bind to `n` for the sequence of 1 ..= 12.
            // Now the age can be reported.
            n @ 1  ..= 12 => println!("I'm a child of age {:?}", n),
            n @ 13 ..= 19 => println!("I'm a teen of age {:?}", n),
            // A similar binding can be done when matching several values.
            n @ (1 | 7 | 15 | 13) => println!("I'm a teen of age {:?}", n),
            // Nothing bound. Return the result.
            n             => println!("I'm an old person of age {:?}", n),
        }
    }

You can also use binding to “destructure” `enum` variants, such as `Option`:

    fn some_number() -> Option<u32> {
        Some(42)
    }

    fn main() {
        match some_number() {
            // Got `Some` variant, match if its value, bound to `n`,
            // is equal to 42.
            // Could also use `Some(42)` and print `"The Answer: 42!"`
            // but that would require changing `42` in 2 spots should
            // you ever wish to change it.
            // Could also use `Some(n) if n == 42` and print `"The Answer: {n}!"`
            // but that would not contribute to exhaustiveness checks.
            // (Although in this case that would not matter since
            // the next arm is a "catch-all" pattern)
            Some(n @ 42) => println!("The Answer: {}!", n),
            // Match any other number.
            Some(n)      => println!("Not interesting... {}", n),
            // Match anything else (`None` variant).
            _            => (),
        }
    }

### Ver también

`functions`, `enums` and `Option`