Value binding
- Rust course
- Beginner
- Lesson 84/115
- 4 min
Bind matched values with pattern variables.
Binding values
Patterns can take values apart (destructure) and bind them to variables. Tuples, structs and enums are unpacked the same way:
let nokta = (3, 0);
match nokta {
(0, 0) => println!("merkez"),
(x, 0) => println!("x ekseni {x}"),
(0, y) => println!("y ekseni {y}"),
(x, y) => println!("{x},{y}"),
}Literal parts narrow the match, variable parts capture the value.
Struct destructuring and @
Struct fields are unpacked by name; .. ignores the remaining fields. name @ pattern both checks the pattern and binds the value:
struct Oyuncu { ad: String, puan: u32 }
let o = Oyuncu { ad: String::from("Ece"), puan: 87 };
match o {
Oyuncu { puan: p @ 80..=100, .. } => println!("usta: {p}"),
Oyuncu { ad, .. } => println!("{ad} çalışmalı"),
}Practice Classify points
Loop over the array [(0, 0), (3, 0), (0, 5), (2, 2)] and classify each point with match: merkez, x ekseni N, y ekseni N or x,y. Print each result on its own line.
Starter code
fn main() {
// buraya yaz
}Sample solution
fn main() {
let noktalar = [(0, 0), (3, 0), (0, 5), (2, 2)];
for n in noktalar {
match n {
(0, 0) => println!("merkez"),
(x, 0) => println!("x ekseni {}", x),
(0, y) => println!("y ekseni {}", y),
(x, y) => println!("{},{}", x, y),
}
}
}Expected output
merkez x ekseni 3 y ekseni 5 2,2
Questions and answers
Review the lesson questions together with their answers. To test yourself, solve the lesson interactively.
1 Which arm does <code>match (0, 7) { (x, 0) => .., (0, y) => .., _ => .. }</code> take?
- (0, y) with y = 7 Correct answer
- (x, 0) with x = 0
- _
- None
Explanation: The first arm doesn't fit because the second element isn't 0; the second arm fits because the first element is 0.
2 Bind the range
match yas {
n ____ 0..=17 => println!("{n}: çocuk"),
n => println!("{n}: yetişkin"),
}match yas {
n @ 0..=17 => println!("{n}: çocuk"),
n => println!("{n}: yetişkin"),
}Explanation: @ both checks the range and binds the matching value to n.
3 Pattern and meaning
| Term | Meaning |
|---|---|
(x, 0) |
Second element 0, x is bound |
Oyuncu { ad, .. } |
Only the ad field |
p @ 80..=100 |
Range + binding |
(_, y) |
The first is ignored |