How to import from a file in a subfolder of src?

Question

I want to split my code into multiple subdirectories of src. Example:

src
  main.rs
  sorting_algorithms
    bubble.rs

bubble.rs contains a function bubble_sort; how do I import it to the main.rs?

Answer 1

The subfolder must be declared as a module. You can do that using 3 different ways:

• Inline: declare the sorting_algorithms module inside your main.rs:

  // In main.rs:
  
  mod sorting_algorithms {
      pub mod bubble;
  }
  

  This is the simplest in my opinion.

• Put a sorting_algorithms.rs into the src folder, with the module declaration:

  // In sorting_algorithms.rs:
  
  pub mod bubble;
  

• Put a mod.rs file with the above content into the subfolder. This is advised against, because it can be confusing to have several mod.rs file to work with.

Answer 2

Rust will recognize a subfolder of src as a module only if you add a mod.rs file to it. Add it to the sorting_algorithms folder:

src
  main.rs
  sorting_algorithms
    bubble.rs
    mod.rs

The mod.rs file can expose a submodule of this folder:

pub mod bubble;

Assuming the function bubble_sort is declared public (pub fn bubble_sort(...)) you will be able to use it from main.rs:

mod sorting_algorithms;
pub use sorting_algorithms::bubble::bubble_sort;