Cozycation

Cozycation - Apartment finder app.

Using providers for state management

Demo

Dependencies

• provider
• google_fonts
• url_launcher
• http

Usage Provider - State Management

Exposing a value

Exposing a new object instance

Providers allow you to not only expose a value, but also create, listen, and dispose of it.

To expose a newly created object, use the default constructor of a provider. Do not use the .value constructor if you want to create an object, or you may otherwise have undesired side effects.

See this StackOverflow answer which explains why using the .value constructor to create values is undesired.

• DO create a new object inside create.

Provider(
  create: (_) => MyModel(),
  child: ...
)

• DON'T use Provider.value to create your object.

ChangeNotifierProvider.value(
  value: MyModel(),
  child: ...
)

• DON'T create your object from variables that can change over time.

  In such a situation, your object would never update when the value changes.

int count;

Provider(
  create: (_) => MyModel(count),
  child: ...
)

If you want to pass variables that can change over time to your object, consider using ProxyProvider:

int count;

ProxyProvider0(
  update: (_, __) => MyModel(count),
  child: ...
)

NOTE:

When using the create/update callback of a provider, it is worth noting that this callback is called lazily by default.

This means that until the value is requested at least once, the create/update callbacks won't be called.

This behavior can be disabled if you want to pre-compute some logic, using the lazy parameter:

MyProvider(
  create: (_) => Something(),
  lazy: false,
)

Reusing an existing object instance:

If you already have an object instance and want to expose it, it would be best to use the .value constructor of a provider.

Failing to do so may call your object dispose method when it is still in use.

• DO use ChangeNotifierProvider.value to provide an existing [ChangeNotifier].

MyChangeNotifier variable;

ChangeNotifierProvider.value(
  value: variable,
  child: ...
)

• DON'T reuse an existing [ChangeNotifier] using the default constructor

MyChangeNotifier variable;

ChangeNotifierProvider(
  create: (_) => variable,
  child: ...
)