Module 3Enums & matchLesson 5 of 922 min

Pattern Matching in Depth

Destructuring, match guards, and readable order-type descriptions.

Patterns cheat sheet

Limit(px) — bind inner data
Stop { trigger, limit } — destructure fields
x if x > 0.0 — guard
_ — ignore

rust

match ot {
    OrderType::Limit(px) if px > 0.0 => format!("LMT {px}"),
    OrderType::Limit(_) => "invalid limit".into(),
    OrderType::Market => "MKT".into(),
    OrderType::Stop { trigger, limit } => format!("STP {trigger}/{limit}"),
}

Nested data

Enums inside structs are normal:

rust

struct Order {
    side: Side,
    kind: OrderType,
}

Exercise

Challenge

Match on (Side, OrderType) pairs and print combined tickets.

Tips

Guards use if after the pattern
Prefer explicit arms over _ in critical logic
Destructure for clarity

Try it live

Pattern Matching in DepthRust 2021

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Output

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