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Dart Flashcards: Fundamentals

Dart — Fundamentals Flashcards

30 interactive flashcards covering core Dart concepts from null safety to Dart 3 features and Flutter basics. Press Space to flip, rate 1-4.

Additional Flashcard Topics

  • Null Safety: String is non-nullable; String? is nullable. The ? suffix, ! (force unwrap), ?? (default), and ?. (safe call) operators handle nullability.

  • Async/Await: async functions return Future<T>. await pauses execution until the Future completes. then() chains async operations. Error handling with try-catch.

  • Records (Dart 3): (int, String) — unnamed, fixed-size collections with named fields. Destructure with var (a, b) = record.

  • Patterns (Dart 3): switch expressions, destructuring, guards. switch (shape) { Circle(r: var radius) => ... }.

  • Mixins: class A extends B with C, D — reuse code across class hierarchies. Mixins can declare on constraints.

  • Isolates: Dart’s concurrency model. Each isolate has its own memory and event loop. Communication via message passing. No shared state.

Intuition

Dart is a client-optimised language for building apps on any platform — it compiles to native code (AOT) for mobile and JavaScript for web. The single-threaded event loop model handles concurrency via async/await and Futures (similar to JavaScript Promises). Null safety, introduced in Dart 2.12, makes every variable non-nullable by default — the ? suffix marks nullable types, and late defers initialisation to runtime. Records and patterns (Dart 3) bring modern data modelling to the language. Dart is the language of Flutter — understanding Dart is essential for Flutter development.

Common Pitfalls

  • Future timing: Starting an async operation without awaiting it — the code continues executing before the Future completes, causing race conditions. Use await or chain with .then().
  • Widget rebuilds: Rebuilding the entire widget tree on state changes in Flutter — use const constructors and targeted state management to minimise rebuilds.
  • Mixin ordering: When using with A, B, the last mixin’s methods take precedence — this can override earlier mixin methods unexpectedly if they share the same method name.
  • Late variable misuse: late defers initialisation but throws LateInitializationError if accessed before being set. Use only when the variable cannot be initialised in the constructor.
  • Double vs double precision: Dart uses 64-bit doubles for all numbers. int and double are separate types — 1.0 is a double, 1 is an int.

Cross-References

  • Dart Practice: Auto-graded problems that test the same concepts covered in these flashcards.
  • Variables: Type specifiers, null safety, and collection types referenced in the flashcards.
  • Async and Futures: Event loop and concurrency model covered in the async flashcards.
  • Classes and Inheritance: OOP patterns including mixins and extension methods.