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Installing a cargo crate

In the previous section of this module, you learned how to create a new cargo project, build, and run it. This section will focus on the [dependencies] section of your Cargo.toml and how to bring in external crates for usage within your project. Crates are other Rust packages with publicly exposed types and functionality for usage in Cargo projects.

Adding a new crate​

Two primary methods of declaring an external crate in Rust are directly putting it in Cargo.toml or using the cargo CLI.

Using Cargo.toml​

We'll be importing the crate called hex. It is a crate that easily encodes and decodes data into hexadecimal representation.

Add this dependency as a key and value under [dependencies], like so:

[dependencies]
hex = "0.4"

The convention is the crate's name, hex, followed by the version of the crate, 0.4. To ensure everything is correctly in place without building the whole project, you may run cargo check:

Checking hex v0.4.3
Checking first-cargo v0.1.0 (/rust-course/first-cargo)
Finished dev [unoptimized + debuginfo] target(s) in 0.70s

Using the cargo CLI​

Optionally, you may also use the CLI to automate this by using cargo add hex:

Updating crates.io index
  Adding hex v0.4.3 to dependencies.
         Features:
         + alloc
         + std
         - serde

This will have the same effect as directly putting it within the TOML file.

For more information regarding Cargo and dependencies, visit the official Cargo documentation.