Enums in Rust
From the Rust cheat sheet · Structs & Enums · verified Jul 2026
Enums
Define enums with variants that can hold data.
rust
// Enum with data variants
enum Shape {
Circle(f64), // radius
Rectangle { width: f64, height: f64 },
Triangle(f64, f64, f64), // sides
}
// Use match to handle variants
fn area(shape: &Shape) -> f64 {
match shape {
Shape::Circle(r) => std::f64::consts::PI * r * r,
Shape::Rectangle { width, height } => width * height,
Shape::Triangle(a, b, c) => { /* ... */ 0.0 }
}
}💡 Option<T> replaces null — Some(value) or None, compiler forces you to handle both
⚡ Use matches!(val, Pattern) for quick boolean pattern checks without a full match
📌 Each enum variant can hold different types and amounts of data — much more powerful than C enums
🟢 .unwrap() panics on None — prefer .unwrap_or(), .map(), or if let in production code
enumsoptionmatchvariants