Rust Programming By Example

Playing with Options

To explain briefly how it works, when the Option type is Some, it simply means it contains a value whereas None doesn't. It has already been explained in Chapter 1, Basics of Rust, but here's a little recap just in case you need one. We can compare this mechanism with pointers in C-like languages; when the pointer is null, there is no data to access. The same goes for None.

Here's a short example:

    fn divide(nb: u32, divider: u32) -> Option<u32> {
      if divider == 0 {
        None
      } else {
          Some(nb / divider)
        }
    }  

So here, if the divider is 0, we can't divide or we'll get an error. Instead of setting an error or returning a complicated type, we just return an Option:

    let x = divide(10, 3);
    let y = divide(10, 0);

Here, x is equal ...