Rust modules

Rust Module System

In Rust, subdirectory under src/ become modules when they contain a mod.rs file. And modules can also be defined in a file with mod keyword. Rust modules can nest arbitrarily:

mod front_of_house {
    pub mod hosting {
        pub fn add_to_waitlist() {}
    }
    mod serving {
        fn take_order() {}
    }
}

We can bring items from other modules into local scope by the use keyword.

All the modules in current crate has the root crate, and we can access modules with absolute paths such as crate::front_of_house::hosting::add_to_waitlist.

We can also refer to modules by relative path:

pub fn eat_at_restaurant() {
    // Relative path
    front_of_house::hosting::add_to_waitlist();
}

All members of a modules are private by default. Prefixing with a pub keyword explicitly make it public, and we can add options after pub:

• pub(crate): public within Rust crate
• pub(super): public within parent module
• pub(in path): public within path
• pub(self): explicitly private