Packages, Crates, Modules

Question 1

How many binary crates can a package contain?

Answer 1

Multiple.

Question 2

How many library crates can a package contain?

Answer 2

One.

Question 3

What is the module system in Rust?

Answer 3

A collection of features that help organize code. Features such as which code details are public or private, and what names in a program are in what scope.

Question 4

What Rust features make up the module system?

Answer 4

Packages, Crates, Modules and Use, Paths.

Question 5

What are packages in Cargo?

Answer 5

A Cargo feature that lets you build, test, and share crates. One or more crates that provide a set of functionality

Question 6

What are crates in Cargo?

Answer 6

A tree of modules that produces a library or executable.

Question 7

What do Modules do?

Answer 7

Organize code within a crate into groups for readability and easy reuse. Modules also control the privacy of items.

Question 8

What are Paths?

Answer 8

A way of naming an item, such as a struct, function, or module.

Question 9

What is the Crate root file?

Answer 9

Source file that the Rust compiler starts from and makes up the root module of your crate.

Question 10

What file does every Package contain?

Answer 10

Cargo.toml

Question 11

What does a Cargo.toml file describe?

Answer 11

How to build the Crates in a package.

Question 12

What must a Package contain?

Answer 12

Zero or one Library crates.

Question 13

What is the command to create a Package?

Answer 13

cargo new

Question 14

What convention does Cargo follow regarding src/main.rs?

Answer 14

src/main.rs is the crate root of a binary crate with the same name as the package.

Question 15

What convention does Cargo follow regarding src/lib.rs?

Answer 15

If the package directory contains src/lib.rs then src/lib.rs is the crate root of a Library crate with the same name as the package.

Question 16

How does cargo build a Library or a Binary?

Answer 16

By passing the crate root to rustc.

Question 17

How does a package create multiple binary crates?

Answer 17

By placing files in the src/bin directory: each file will be a separate binary crate.

Question 18

What is the syntax for defining a module?

Answer 18

mod {}

Question 19

What do the contents of src/main.rs and src/lib.rs form?

Answer 19

A module named crate at the root of the crate’s module structure, known as the module tree.

Question 20

What does Rust use to find an item in a module tree?

Answer 20

A path.

Question 21

What are the two forms a path can take?

Answer 21

An absolute or a relative path.

Question 22

What is an absolute path in Rust?

Answer 22

Path that starts from a crate root by using a crate name or a literal crate.

Question 23

What is a relative path in Rust?

Answer 23

Path that starts from the current module and uses self, super, or an identifier in the current module.

Question 24

What defines Rusts privacy boundary?

Answer 24

A module.

Question 25

Are all items in Rust private by default?

Answer 25

Yes.

Question 26

How can you expose inner parts of child modules code to outer ancestor modules?

Answer 26

Using the pub keyword to make an item public.

Question 27

What does the pub keyword on a module do?

Answer 27

Lets code in its ancestor module refer to it.

Question 28

What does using super at the start of a path do?

Answer 28

Constructs a relative path that begins in the parent module.

Question 29

What does pub before a struct definition do?

Answer 29

Make the struct public. The struct fields will still be private.

Question 30

What does adding pub to an enum definition do?

Answer 30

Makes it public, along with ALL its variants.

Question 31

How do we bring path items into scope?

Answer 31

With the keyword use.

Question 32

How does using the use keyword with a relative path differ from using it with an absolute path?

Answer 32

The relative path must start with the keyword self.

Question 33

What is the idiomatic way to bring a function into scope with the keyword use?

Answer 33

Bringing the functions parent module into scope, and not the function itself.

Question 34

What is the idiomatic way to bring structs, enums, and other items besides functions into scope with the keyword use?

Answer 34

By specifying the full path.

Question 35

What is the as keyword used for in Rust?

Answer 35

To provide an alias for an import or cast between types.

Question 36

What is re-exporting?

Answer 36

Using pub and use to bring an item into scope but also making that item available for others to bring into their scope.