Crate skeleton

Set up a library crate with lib.rs.

Library project: skeleton

In this project we'll write a small library crate that keeps books on a shelf and searches them. A library crate offers an API for others to use instead of a main:

$ cargo new --lib kitaplik
$ tree kitaplik
kitaplik
├── Cargo.toml
└── src
    └── lib.rs

In the exercises we'll write everything in a single file, inside a mod kitaplik { .. } block; in a real project this content lives in src/lib.rs and is used from outside with use kitaplik::Kitap;.

Modules and visibility

Everything inside a module is private by default. Items to be used from outside are marked with pub; even if the struct itself is pub, its fields must also be pub:

mod kitaplik {
    pub struct Kitap {
        pub ad: String,
        pub yazar: String,
        pub yil: u16,
    }
}

use kitaplik::Kitap;

In the first version we leave the fields open; in the next lesson we'll encapsulate the API.

Exercise First book

Inside mod kitaplik, define Kitap { ad: String, yazar: String, yil: u16 } with pub fields. In main, bring it in with use, create the book Tutunamayanlar / Oğuz Atay / 1972 and print it as ad - yazar (yil).

Show example solution

mod kitaplik {
    pub struct Kitap {
        pub ad: String,
        pub yazar: String,
        pub yil: u16,
    }
}

use kitaplik::Kitap;

fn main() {
    let k = Kitap {
        ad: String::from("Tutunamayanlar"),
        yazar: String::from("Oğuz Atay"),
        yil: 1972,
    };
    println!("{} - {} ({})", k.ad, k.yazar, k.yil);
}

Test yourself

Which file does <code>cargo new --lib</code> create?
- src/main.rs
- lib/mod.rs
- src/kitaplik.rs
- src/lib.rs
Show answer

src/lib.rs — A library crate's root is src/lib.rs, a binary crate's root is src/main.rs. A package can contain both.

Make it public

mod kitaplik {
    ____ struct Kitap {
        pub ad: String,
    }
}

Show answer

mod kitaplik {
    pub struct Kitap {
        pub ad: String,
    }
}

Item and visibility

struct Kitap (no pub)

Module only
pub struct Kitap

Type visible outside
pub ad: String

Field visible outside
use kitaplik::Kitap

Brings into scope

Next lesson: Public API

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