Packages, Crates, and Modules

Definitions

• Packages - A Cargo feature that lets you build, test, and share crates.
• Crates - A tree of modules that produces a library or executable.
• Modules and use - Let you control the organization, scope, and privacy of paths.
• Paths - A way of naming an item, such as a struct, function, or module.

Creating a new package with a binary crate

    cargo new my-project

Creating a new package with a library crate

cargo new my-project --lib

Defining and using modules

fn some_function() {}
mod outer_module { // private module
    pub mod inner_module { // public module
        pub fn inner_public_function() {
            super::super::some_function();
        }
        fn inner_private_function() {}
    }
}

fn main() {
    // absolute path
    crate::outer_module::
    inner_module::inner_public_function();

    // relative path path
    outer_module::
    inner_module::inner_public_function();
    
    // bringing path into scope
    use outer_module::inner_module;
    inner_module::inner_public_function();
}

Renaming with as keyword

use std::fmt::Result;
use std::io::Result as IoResult;

Re-exporting with pub use

mod outer_module {
    pub mod inner_module {
        pub fn inner_public_function() {}
    }
}
pub use crate::outer_module::inner_module;

Defining modules in separate files

// src/lib.rs
mod my_module;
pub fn some_function() {
my_module::my_function();
}
// src/my_module.rs
pub fn my_function() {}