Use module from parent directory in rust

Question

Is it possible to structure a rust project in this way?

Directory structure:

src
├── a
│   └── bin1.rs
├── b
│   ├── bin2.rs
└── common
    ├── mod.rs

from Cargo.toml:

[[bin]]
name = "bin1"
path = "src/a/bin1.rs"

[[bin]]
name = "bin2"
path = "src/b/bin2.rs"

I would like to be able to use the common module in bin1.rs and bin2.rs. It's possible by adding the path attribute before the import:

#[path="../common/mod.rs"]
mod code;

Is there a way for bin1.rs and bin2.rs to use common without having to hardcode the path?

Alice Ryhl · Accepted Answer · 2020-01-26 08:18:04Z

16

The recommended method to share code between binaries is to have a src/lib.rs file. Both binaries automatically have access to anything accessible through this lib.rs file as a separate crate.

Then you would simply define a mod common; in the src/lib.rs file. If your crate is called my_crate, your binaries would be able to use it with

use my_crate::common::Foo;

answered Jan 26, 2020 at 8:18

Alice Ryhl

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4 Comments

Anselan Over a year ago

This helped me enormously. I have also seen something like use crate:: ... which I thought might refer to "whatever the root crate is" but that returns a compiler error "no X in the root" (where X is my module name). What is the "root" crate, then?

Alice Ryhl Over a year ago

You should think of lib.rs and main.rs as the roots of two entirely distinct crates. When accessing something inside the same crate, you use use crate::, and when accessing something in lib.rs from main.rs, you use use my_crate::. There is no way to access something from main.rs in the lib.rs crate.

Qwertie Over a year ago

Where is the 'my_crate' name determined? The name in cargo.toml?

Alice Ryhl Over a year ago

Yes, it's taken from your Cargo.toml.

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