freezed_weather

A rewrite of Bloc tutorial: Flutter Weather Tutorial using freezed.

• Bloc is used instead of Cubit (Cubit vs Bloc)
  • Bloc provides better traceability of what's happening.
    • onTransition shows the event that triggers the new state
  • Bloc allows advanced event transformations
  • However, bloc requires more detailed implementation. freezed code generation could be used to reduce the amount of coding.
• freezed is used to compare data models. equatable is not used anymore.
  • A @freezed class comes with generated copyWith implementation, which is not prone to human-made errors (e.g., forget to add a variable into prop list, which is the mistake I've made).

Notable changes

@freezed data models

• copyWith, == and toString implementation

• Properties can be null

  Previously, Weather.empty is provided in initial WeatherState because equatable does not allow null in props. freezed handles null properly so we can just use null as weather in the state when weather is not available yet (e.g., in the initial state). Both work fine, it's only a matter of choice so empty is kept in lib/weather/models/weather.dart.

@freezed event & state for bloc

Persist only the loaded state

In the original tutorial, all states are cached. Imagine the scenario: When an error happens, the user terminates the app and reopens it. Guess what? The error state is served immediately!

The bloc is working properly but the user experience is not optimal. WeatherBloc.toJson is modified to only cache the successfully loaded state. When the user opens the app, it always shows that last loaded weather (or the initial state if nothing happens yet). Again, it's a matter of choice of when to cache the states.

Cautions

This tutorial has been rewritten after the releases of Flutter 3.0, freezed 2.0.3, and hydrated_bloc 9.0.0-dev.2. It won't work on previous versions. You can use tag 1.0 to fetch the older scripts.