aliases for Result - Rust By Example
Description: A description

# aliases for `Result`

How about when we want to reuse a specific `Result` type many times? Recall that Rust allows us to create aliases. Conveniently, we can define one for the specific `Result` in question.

At a module level, creating aliases can be particularly helpful. Errors found in a specific module often have the same `Err` type, so a single alias can succinctly define all associated `Results`. This is so useful that the `std` library even supplies one: `io::Result`!

Here's a quick example to show off the syntax:

    use std::num::ParseIntError;

    // Define a generic alias for a `Result` with the error type `ParseIntError`.
    type AliasedResult<T> = Result<T, ParseIntError>;

    // Use the above alias to refer to our specific `Result` type.
    fn multiply(first_number_str: &str, second_number_str: &str) -> AliasedResult<i32> {
        first_number_str.parse::<i32>().and_then(|first_number| {
            second_number_str.parse::<i32>().map(|second_number| first_number * second_number)
        })
    }

    // Here, the alias again allows us to save some space.
    fn print(result: AliasedResult<i32>) {
        match result {
            Ok(n)  => println!("n is {}", n),
            Err(e) => println!("Error: {}", e),
        }
    }

    fn main() {
        print(multiply("10", "2"));
        print(multiply("t", "2"));
    }

### See also:

`io::Result`