Static - Rust By Example
Description: A description

# Static

A `'static` lifetime is the longest possible lifetime, and lasts for the lifetime of the running program. A `'static` lifetime may also be coerced to a shorter lifetime. There are two ways to make a variable with `'static` lifetime, and both are stored in the read-only memory of the binary:

- Make a constant with the `static` declaration.
- Make a `string` literal which has type: `&'static str`.

See the following example for a display of each method:

    // Make a constant with `'static` lifetime.
    static NUM: i32 = 18;

    // Returns a reference to `NUM` where its `'static`
    // lifetime is coerced to that of the input argument.
    fn coerce_static<'a>(_: &'a i32) -> &'a i32 {
        &NUM
    }

    fn main() {
        {
            // Make a `string` literal and print it:
            let static_string = "I'm in read-only memory";
            println!("static_string: {}", static_string);

            // When `static_string` goes out of scope, the reference
            // can no longer be used, but the data remains in the binary.
        }

        {
            // Make an integer to use for `coerce_static`:
            let lifetime_num = 9;

            // Coerce `NUM` to lifetime of `lifetime_num`:
            let coerced_static = coerce_static(&lifetime_num);

            println!("coerced_static: {}", coerced_static);
        }

        println!("NUM: {} stays accessible!", NUM);
    }

### See also:

`'static` constants