The Complete Rust Programming Reference Guide

File as a module

Modules can also be created as files. For instance, for a main.rs file in a directory named foo, we can create a module bar as a file in the same directory as foo/bar.rs. Then in main.rs, we need to tell the compiler of this module, that is, declare the module with mod foo;. This is an extra step when using file-based modules. To demonstrate using a file as a module, we have created a directory named modules_demo, which has the following structure:

+ modules_demo└── foo.rs└── main.rs

Our foo.rs contains a struct Bar, with its impl block:

// modules_demo/foo.rspub struct Bar;impl Bar {    pub fn init() {        println!("Bar type initialized");    }}

We want to use this module in main.rs. Our main.rs, has the following code:

// modules_demo/main.rs ...