Cargo.toml

Add dependencies with Cargo.toml.

Cargo.toml

Cargo.toml defines the package's identity and dependencies. It's in TOML format: [section] headers and key = value lines:

[package]
name = "fatura"
version = "0.1.0"
edition = "2021"

[dependencies]
serde = { version = "1", features = ["derive"] }
rand = "0.8"

[dev-dependencies]
pretty_assertions = "1"

edition decides which edition's rules the language is compiled with (2015, 2018, 2021, 2024); crates on different editions work together.

Cargo.lock

Cargo.lock records the exact version of every resolved dependency, so everyone gets the same build. In binary projects it's committed to version control. cargo update moves to the newest versions within the allowed range, and cargo add serde adds a dependency to Cargo.toml.

$ cargo add rand
$ cargo tree        # dependency tree
$ cargo update -p rand

Exercise Read a TOML line

Split the text let girdi = "edition = \"2021\""; with split_once('='), trim both sides and remove the quotes from the value with trim_matches('"'). Print it as edition: 2021.

Show example solution

fn main() {
    let girdi = "edition = \"2021\"";
    let (anahtar, deger) = girdi.split_once('=').unwrap();
    let anahtar = anahtar.trim();
    let deger = deger.trim().trim_matches('"');
    println!("{}: {}", anahtar, deger);
}

Test yourself

When are dependencies under <code>[dev-dependencies]</code> compiled?
- In every build
- Only in a release build
- Never
- Only for tests, examples and benchmarks
Show answer

Only for tests, examples and benchmarks — Users of the library don't download dev-dependencies; ideal for test tools.

Dependency section

[____]
rand = "0.8"

Show answer

[dependencies]
rand = "0.8"

Key and meaning

name

Package name
version

Package version
edition

Language edition rules
[dev-dependencies]

Test dependencies

Next lesson: Versions

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