Dart cheat sheet

A scannable Dart reference: 7 short snippets across 5 topics, each linking back to the lesson it came from.

At a glance

Topic	What it covers
Isolates, compilation and packaging	Each isolate runs on a single thread with two queues: microtasks, which drain completely before the loop continues, and	lesson
Packages, pubspec and project layout	Write a pubspec, manage version constraints and lock files, structure a package, and know what publishing requires	lesson
Testing Dart code	expectLater returns a Future that must be awaited, which is what makes completion and emits reliable. Forgetting the	lesson
Command-line tools: args, stdin and exit codes	A tool that reports a failure in its log and still exits 0 is unusable in a pipeline. The exit code is the interface	lesson
From Dart to Flutter	The single most common Flutter bug is creating a Future or a controller inside build. Every rebuild starts a new	lesson

Quick snippets

Isolates, compilation and packaging

Packaging and compilation

# pubspec.yaml
name: my_tool
description: A small command line tool.
version: 0.1.0
environment:
  sdk: ^3.5.0
dependencies:
  http: ^1.2.0
dev_dependencies:
  test: ^1.25.0
  lints: ^4.0.0

Packaging and compilation

dart pub get                      # resolve pubspec.lock
dart pub add http                 # add and record a dependency
dart pub upgrade --major-versions # move constraints forward
dart analyze                      # static checks
dart format .                     # rewrite to canonical style
dart test                         # run the test/ directory

dart run bin/my_tool.dart         # JIT, fast startup during development
dart compile exe bin/my_tool.dart -o build/my_tool   # native AOT
dart compile js web/main.dart -o build/main.js       # for the browser
dart pub publish --dry-run        # check before publishing

Full lesson: Isolates, compilation and packaging →

Packages, pubspec and project layout

The pubspec

dart pub get                  # resolve and write pubspec.lock
dart pub upgrade              # move to the newest allowed versions
dart pub upgrade --major-versions
dart pub outdated             # what is behind, and whether it is safe to move
dart pub add http             # edit the pubspec and resolve
dart pub deps --style=compact
dart pub publish --dry-run    # validate before publishing
dart pub cache repair         # fix a corrupted package cache

Layout and visibility

// lib/shop_core.dart — the public surface
/// Pricing rules and domain models for the shop.
library;

export 'src/money.dart' show Money;
export 'src/pricing.dart' show PricingRule, applyRules;
// src/internal/rounding.dart is deliberately not exported.

// Because everything outside lib/src is importable by convention,
// dart's linter warns when a consumer imports package:shop_core/src/...
// The src/ directory is the community agreement for "private to this package".

Full lesson: Packages, pubspec and project layout →

Testing Dart code

Fakes, mocks and integration

dart test
dart test test/money_test.dart
dart test --name "currency"
dart test --coverage=coverage
dart run coverage:format_coverage --lcov --in=coverage --out=coverage/lcov.info
dart test -p vm,chrome          # run on several platforms

Full lesson: Testing Dart code →

Command-line tools: args, stdin and exit codes

Compiling and shipping an executable

# to publish the tool so others can run it with dart pub global activate
executables:
  shop: shop

Full lesson: Command-line tools: args, stdin and exit codes →

From Dart to Flutter

What changes in the toolchain

flutter doctor                  # check the SDK, the toolchains and the devices
flutter create my_app
flutter pub get
flutter run -d chrome
flutter test
flutter analyze
flutter build apk --release
flutter build web --release
flutter pub run build_runner build --delete-conflicting-outputs

Full lesson: From Dart to Flutter →

FAQ

Is this Dart cheat sheet free to use?

Yes. No sign-up and no tracking: the page is static, every example is on the page itself, and you can print it or save it as a one-page reference.

Where do the examples come from?

Every snippet is taken from the 5 lessons of the Dart course on this site, and each section links back to the lesson it was pulled from.

How do I go deeper than a cheat sheet?

Open the full Dart course — it carries the worked explanations, the edge cases and the exercises behind every line here.

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Last refreshed 2026-09-27.