How to use the command 'cargo add' (with examples)

The ‘cargo add’ command is a tool in Rust’s package manager, Cargo, that allows you to add dependencies to your project’s Cargo.toml manifest. It simplifies the process of managing dependencies and ensures that all necessary libraries are included in your project.

Use case 1: Add the latest version of a dependency to the current project

Code:

cargo add dependency

Motivation: The motivation for using this example is to quickly add the latest version of a dependency to your project without having to specify a specific version. This is useful when you want to ensure you are always using the most up-to-date version of a library.

Explanation: In this example, ‘dependency’ refers to the name of the dependency you want to add. By running this command, Cargo will automatically fetch and add the latest version of the specified dependency to your project’s Cargo.toml file.

Example output:

Adding dependency v0.1.2 to Cargo.toml.

Use case 2: Add a specific version of a dependency

Code:

cargo add dependency@version

Motivation: This example is useful when you explicitly need to use a specific version of a dependency. It allows you to ensure your project is compatible with a particular version of a library.

Explanation: In this example, ‘dependency’ refers to the name of the dependency, and ‘version’ refers to the specific version number you want to add. By including ‘@’ followed by the version number, Cargo will add the specified version of the dependency to your project’s Cargo.toml file.

Example output:

Adding dependency v0.3.1 to Cargo.toml.

Use case 3: Add a dependency and enable one or more specific features

Code:

cargo add dependency --features feature_1,feature_2

Motivation: This example allows you to add a dependency to your project and enable specific features provided by that dependency. This is useful when you want to leverage additional functionality provided by the library.

Explanation: In this example, ‘dependency’ refers to the name of the dependency, and ‘feature_1’ and ‘feature_2’ refer to the specific features you want to enable. By including ‘–features’ followed by the feature names separated by commas, Cargo will add the dependency to your project with the specified features enabled.

Example output:

Adding dependency v0.2.0 to Cargo.toml with features: feature_1, feature_2.

Use case 4: Add an optional dependency, which then gets exposed as a feature of the crate

Code:

cargo add dependency --optional

Motivation: This example is useful when you want to add an optional dependency to your project that exposes an additional feature as a crate. It allows you to include functionality in your project that is only necessary in certain scenarios.

Explanation: In this example, ‘dependency’ refers to the name of the optional dependency you want to add. By including ‘–optional’ in the command, Cargo will add the dependency to your project with the appropriate configuration, exposing it as a feature of the crate.

Example output:

Adding optional dependency v0.4.5 to Cargo.toml as a feature of the crate.

Use case 5: Add a local crate as a dependency

Code:

cargo add --path path/to/crate_directory

Motivation: This example is useful when you want to add a local crate as a dependency to your project. It allows you to develop different parts of your project separately and then easily integrate them as dependencies.

Explanation: In this example, ‘path/to/crate_directory’ should be replaced with the actual path to the local crate directory. By using the ‘–path’ argument followed by the path to the crate, Cargo will add the local crate as a dependency to your project’s Cargo.toml file.

Example output:

Adding local crate at path/to/crate_directory to Cargo.toml.

Use case 6: Add a development or build dependency

Code:

cargo add dependency --dev|build

Motivation: This example is useful when you need to add a dependency that is only required during development or build processes. It allows you to separate the dependencies needed for different stages of your project.

Explanation: In this example, ‘dependency’ refers to the name of the development or build dependency you want to add. By including ‘–dev’ or ‘–build’ in the command, Cargo will add the dependency to the appropriate section in your project’s Cargo.toml file.

Example output:

Adding development dependency v0.5.0 to Cargo.toml.

Use case 7: Add a dependency with all default features disabled

Code:

cargo add dependency --no-default-features

Motivation: This example is useful when you want to add a dependency to your project but disable all of its default features. It allows you to selectively enable only the features you need, reducing the overall size and complexity of your project.

Explanation: In this example, ‘dependency’ refers to the name of the dependency. By including ‘–no-default-features’ in the command, Cargo will add the dependency to your project with all of its default features disabled.

Example output:

Adding dependency v0.6.2 to Cargo.toml with all default features disabled.

Conclusion:

The ‘cargo add’ command is a powerful tool in Rust’s package manager, Cargo, that simplifies the process of adding dependencies to your project’s Cargo.toml manifest. By using the various arguments and options, you can easily manage dependencies and include the necessary libraries in your Rust project.