Rust Programming By Example

Builder pattern

A builder pattern is meant to be able to build a final object through multiple calls that can be chained. An excellent example is the OpenOptions type in the Rust standard library.

It's strongly recommended you use OpenOptions when you need to play with File!

use std::fs::OpenOptions;

let file = OpenOptions::new()
                       .read(true)
                       .write(true)
                       .create(true)
                       .open("foo.txt");

To make such APIs, you have two ways:

• Playing with mutable borrows
• Playing with moves

Let's start with the mutable borrows!