Tag: dart

FutureBuilder re-runs your async work every time the parent rebuilds because you created the Future inside build. Hoist it into State.initState (or memoize it), and FutureBuilder will reuse the same Future. Here is the why, the repro, and every variant that bites.

Dart 3.12 adds an experimental primary constructors syntax that declares fields and a constructor in the class header, collapsing the classic three-line data class to one.

Pick Riverpod for most new Flutter apps in 2026. Choose Bloc for large teams that want an enforced event-driven structure, and keep Provider only for legacy code.

RenderBox was not laid out is almost always a secondary error. Find the first layout assertion above it, usually a scrollable given unbounded constraints, and fix that.

This crash means code touched a controller after dispose() ran. Guard async callbacks with a mounted check, and never dispose a controller you do not own.

This error means you mutated state while Flutter was building. Move the setState out of build, or defer it with addPostFrameCallback. Here is why it happens and the right fix.

Render loading, data, and error UI from a single AsyncValue in Riverpod 3. Use AsyncNotifier and AsyncValue.guard for mutations, .when() and switch pattern matching for the UI, keep previous data on refresh, and migrate the legacy StateNotifier pattern. Tested on flutter_riverpod 3.x, Flutter 3.44, Dart 3.x.

AnimationController, TextEditingController, and ScrollController hold resources that Dart's GC cannot reclaim until you dispose them. Here is the correct pattern, the ordering rules, and how to catch leaks before they ship.

A request can fail with no connectivity, a timeout, a DNS failure, a 500, or malformed JSON, and each needs a different response. Here is how to catch the right exceptions, classify them, retry safely, and show a UI a user can act on.

Dart 3.12 ships dart mcp-server, the official MCP bridge into the Dart and Flutter toolchain. Register it once in Claude Code, Cursor, or Codex CLI and your agent gets hot reload, pub.dev search, and live widget introspection without copy-pasting a DTD URI.