Python Pattern Matching & Destructuring in Dart 3
Pattern Matching in Dart 3 enables expressive data destructuring and validation. Patterns match values against shapes, extract subcomponents into local variables, and assert conditions simultaneously. You can destructure Lists, Records, Maps, Object properties, and apply Relational Patterns (`>= 100`, `< 0`).
"Pattern matching is like a coin sorter: coins roll down a slot where each coin fits into a matching hole and drops into a categorized sorting bin automatically."
Deep Dive: How It Works
List Patterns: `final [first, second, ...rest] = items;` extracts elements and gathers remaining items.
Record Destructuring: `final (name, age: userAge) = ("Alice", age: 30);`.
Relational Patterns: `case >= 18 && <= 65 => "Working Age"` matches numeric ranges directly in switch blocks.
Object Patterns: `case User(role: "admin", :email) => print("Admin: $email");`.
Syntax Blueprint
// List destructuring
final [a, b, ...tail] = [1, 2, 3, 4, 5];
// Relational switch pattern
final desc = switch (score) {
>= 90 => "A",
>= 80 => "B",
_ => "F",
};Destructuring sequences and matching relational boundary patterns.
Core Rules to Remember
Common Beginner Traps & How to Fix Them
Trying to match a fixed-length list pattern against a list with different item counts without `...`.Why it happens: `[a, b]` expects exactly 2 elements; if the list has 3, the match fails.
How to fix: Use `[a, b, ...]` or `if-case` matching.
Live Interactive Example
Hit Run Code to see it liveYour Turn: Micro Challenge
No pressure! Edit the starter code below and test your solution with instant feedback.
Destructure First and Last with Rest Pattern
- Given list `final scores = [100, 85, 90, 70, 95];`.
- Use list pattern destructuring `final [first, ..., last] = scores;`.
- Print `First: $first, Last: $last`.
Finished reading and practicing?
Mark this lesson as completed to update your course progress.