Flutter & Dart Glossary

Dart Language

var — Declares a variable with inferred type. Once assigned, the type is fixed.
final — A variable that can only be set once. The value is determined at runtime.
const — A compile-time constant. The value must be known before the program runs.
dynamic — Opts out of static type checking. The variable can hold any type.
late — Defers initialization of a non-nullable variable until it is first accessed.
typedef — Creates a named alias for a function type or other type.

async / await — Marks a function as asynchronous and pauses execution until a Future completes.
Future — Represents a value that will be available at some point in the future. The core unit of async programming in Dart.
Stream — A sequence of asynchronous events. Use await for or .listen() to consume values over time.
yield — Used inside a generator function (sync* or async*) to emit values one at a time.
Isolate — A separate thread of execution with its own memory. Dart uses isolates instead of shared-memory threads.

class — A blueprint for creating objects. Defines fields, methods, and constructors.
mixin — A way to reuse code across multiple class hierarchies using with.
abstract class — A class that cannot be instantiated directly. Used to define interfaces and shared behavior.
extension — Adds new methods to an existing type without modifying its source.
enum — A fixed set of named constant values.
sealed class — A class that can only be extended within the same library, enabling exhaustive pattern matching.

Widget — The fundamental building block of a Flutter UI. Everything visible on screen is a widget.
Widget Tree — The hierarchical structure of nested widgets that describes the UI.
Element — The instantiation of a widget in the tree. Manages the lifecycle and links widgets to render objects.
RenderObject — The object that handles layout, painting, and hit-testing. Sits behind the element tree.
BuildContext — A handle to the location of a widget in the widget tree. Used to look up inherited data and navigate.
Key — An identifier that helps Flutter match widgets across rebuilds. Important for lists and animations.

StatelessWidget — A widget with no mutable state. Its build method is a pure function of its constructor arguments.
StatefulWidget — A widget that holds mutable state via a companion State object.
State — The mutable companion to a StatefulWidget. Persists across rebuilds.
setState() — Tells the framework that state has changed and the widget needs to rebuild.
initState() — Called once when the State object is first inserted into the tree.
dispose() — Called when the State object is permanently removed. Use it to clean up controllers, subscriptions, and timers.
didChangeDependencies() — Called when an InheritedWidget that this state depends on changes.

Container — A convenience widget that combines padding, margins, decoration, and sizing.
Row — Lays out children horizontally in a line.
Column — Lays out children vertically in a line.
Stack — Layers children on top of each other, with positioning via Positioned.
Expanded — Fills remaining space along the main axis inside a Row or Column.
Flexible — Like Expanded but allows the child to be smaller than the available space.
SizedBox — Forces a child to a specific width and/or height. Also useful as whitespace.
Padding — Adds empty space around a child widget.
Wrap — Lays out children in a row, wrapping to the next line when space runs out.
ListView — A scrollable list of widgets. Use ListView.builder for large or dynamic lists.
GridView — A scrollable 2D grid of widgets.
Scaffold — The basic Material Design page structure: AppBar, body, FloatingActionButton, drawers, and more.

InheritedWidget — A widget that efficiently passes data down the tree. The foundation for Provider and other state solutions.
Provider — A popular package that wraps InheritedWidget for simpler dependency injection and state management.
ChangeNotifier — A class that notifies listeners when its data changes. Commonly used with Provider.
Riverpod — A compile-safe, testable state management library. The spiritual successor to Provider.
Bloc / Cubit — A pattern and library that separates business logic from UI using events and states.
ValueNotifier — A simple ChangeNotifier that holds a single value and notifies when it changes.

Navigator — The widget that manages a stack of Route objects for screen transitions.
MaterialPageRoute — A route that transitions using Material Design animations.
GoRouter — A declarative routing package that uses URL-based paths, popular for web and deep linking.
push / pop — Navigator methods to add a new route to the stack or remove the current one.
Named Routes — Routes identified by string names, configured in MaterialApp.routes.

Widget Test — Tests that build a widget in a test environment and verify its behavior using WidgetTester.
Unit Test — Tests that verify pure Dart logic without any Flutter framework involvement.
Integration Test — Tests that run on a real device or emulator and exercise the full app.
pump() — Triggers a frame rebuild in widget tests. Use pumpAndSettle() to wait for all animations.
Finder — Objects like find.text() and find.byType() used to locate widgets in tests.

pub.dev — The official package repository for Dart and Flutter packages.
pubspec.yaml — The project configuration file that declares dependencies, assets, and metadata.
flutter pub get — Downloads and resolves all dependencies listed in pubspec.yaml.
DevTools — A suite of debugging and profiling tools for Flutter apps (widget inspector, timeline, memory).
Hot Reload — Injects updated source code into a running app without losing state. One of Flutter's killer features.
Hot Restart — Rebuilds the app from scratch, resetting all state. Slower than hot reload but handles structural changes.

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