Rust by Example

fn main() {

// Create struct with field init shorthand

let name = String::from("Peter");

let age = 27;

let peter = Person { name, age };

// Print debug struct

println!("{:?}", peter);

// Instantiate a `Point`

let point: Point = Point { x: 10.3, y: 0.4 };

// Access the fields of the point

println!("point coordinates: ({}, {})", point.x, point.y);

// Make a new point by using struct update syntax to use the fields of our

// other one

let bottom_right = Point { x: 5.2, ..point };

// `bottom_right.y` will be the same as `point.y` because we used that field

// from `point`

println!("second point: ({}, {})", bottom_right.x, bottom_right.y);

// Destructure the point using a `let` binding

let Point { x: top_edge, y: left_edge } = point;

let _rectangle = Rectangle {

// struct instantiation is an expression too

top_left: Point { x: left_edge, y: top_edge },

bottom_right: bottom_right,

};

// Instantiate a unit struct

let _unit = Unit;

// Instantiate a tuple struct

let pair = Pair(1, 0.1);

// Access the fields of a tuple struct

println!("pair contains {:?} and {:?}", pair.0, pair.1);

// Destructure a tuple struct

let Pair(integer, decimal) = pair;

println!("pair contains {:?} and {:?}", integer, decimal);

}

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Activity

   1. Add a function rect_area which calculates the area of a rectangle (try using nested destructuring).

   2. Add a function square which takes a Point and a f32 as arguments, and returns a Rectangle with its lower left corner on the point, and a width and height corresponding to the f32.

See also

attributes, and destructuring

Enums

The enum keyword allows the creation of a type which may be one of a few different variants. Any variant which is valid as a struct is also valid as an enum.

// Create an `enum` to classify a web event. Note how both

// names and type information together specify the variant:

// `PageLoad != PageUnload` and `KeyPress(char) != Paste(String)`.

// Each is different and independent.

enum WebEvent {

// An `enum` may either be `unit-like`,

PageLoad,

PageUnload,

// like tuple structs,

KeyPress(char),

Paste(String),

// or c-like structures.

Click { x: i64, y: i64 },

}

// A function which takes a `WebEvent` enum as an argument and

// returns nothing.

fn inspect(event: WebEvent) {

match event {