Python Switch Statements, Switch Expressions & Exhaustiveness
Dart 3 revolutionized `switch` with pattern matching and Switch Expressions (`=>`). Unlike traditional switch statements that require verbose `case` and `break` keywords, switch expressions return values directly, require no `break` statements, and enforce compile-time exhaustiveness checking (guaranteeing all enum or sealed class cases are handled).
"A switch expression is like a vending machine button panel: you press button "B4" and a snack drops directly into the dispenser tray in a single motion."
Deep Dive: How It Works
Switch Expressions: `final label = switch (status) { Status.ok => "Success", Status.err => "Failed" };`.
Exhaustiveness Checking: The compiler verifies at build-time that every possible enum variant or sealed class subtype is covered.
Pattern Matching & Guards: `case int n when n > 100 => "Large"`.
Syntax Blueprint
// Dart 3 Switch Expression
final label = switch (role) {
"admin" => "Administrator",
"editor" => "Content Editor",
_ => "Standard User",
};Modern concise switch expression with wildcard fallback.
Core Rules to Remember
Common Beginner Traps & How to Fix Them
Adding `break;` inside a modern Dart 3 switch expression.Why it happens: Habit from classic C/Java switch statements.
How to fix: Switch expressions use `pattern => value,` syntax and do not use break.
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.
Evaluate Day Category with Switch Expression
- Given `String day = "SAT";`.
- Use a switch expression to assign `final category = switch (day) { "SAT" || "SUN" => "Weekend", _ => "Weekday" };`.
- Print `Category: $category`.
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