Structures
There are three types of structures (“structs”) that can be created using thestruct
keyword:
- Tuple structs, which are, basically, named tuples.
- The classic C structs
- Unit structs, which are field-less, are useful for generics.
#[derive(Debug)]
struct Person<'a> {
name: &'a str,
age: u8,
}
// A unit struct
struct Nil;
// A tuple struct
struct Pair(i32, f32);
// A struct with two fields
struct Point {
x: f32,
y: f32,
}
// Structs can be reused as fields of another struct
#[allow(dead_code)]
struct Rectangle {
p1: Point,
p2: Point,
}
fn main() {
// Create struct with field init shorthand
let name = "Peter";
let age = 27;
let peter = Person { name, age };
// Print debug struct
println!("{:?}", peter);
// Instantiate a `Point`
let point: Point = Point { x: 0.3, 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 new_point = Point { x: 0.1, ..point };
// `new_point.y` will be the same as `point.y` because we used that field from `point`
println!("second point: ({}, {})", new_point.x, new_point.y);
// Destructure the point using a `let` binding
let Point { x: my_x, y: my_y } = point;
let _rectangle = Rectangle {
// struct instantiation is an expression too
p1: Point { x: my_y, y: my_x },
p2: point,
};
// Instantiate a unit struct
let _nil = Nil;
// 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);
}
Activity
- Add a function
rect_area
which calculates the area of a rectangle (try
using nested destructuring). - Add a function
square
which takes aPoint
and af32
as arguments, and returns aRectangle
with its lower left corner on the point, and a width and height corresponding to thef32
.