functions.md

Functions

Consider extracting intermediates when dealing with long method chains and iterators.

When possible, method paths should be used instead of closures as method parameters.

Example

Don't do:

let result = vec
    .iter()
    .map(|number| u8::from(number))
    .filter(|number| number % 2 == 0)
    .map(|number| number * 2);

Do instead:

let even = vec.iter().map(u8::from).filter(|number| number % 2 == 0);
let result = even.map(|number| number * 2);

Explanation

Not only does extraction of intermediates allow method chains to use less vertical space, it also makes it possible for readers to understand what the purpose of different sub-sections of the chain is by assigning it a meaningful variable name.

Using method paths as function parameters can help significantly shorten some function calls, though is rarely worth it when the path is longer than the closure. Using Option/Result::as_deref can help transform more function calls into the path-parameter form.