Flutter: Why is Provider a better option than a class called AppGlobal with only static singletons?

Question

From what I understand about the flutter package, Provider, is that it's a way to share objects between widgets. I know another way of doing this is to create a class, say AppGlobal, and define various static variables that the whole app could use. It's suggested that Provider is a better way of doing that, but I don't understand why that is.

Answer 1

An answer to the question should take different aspects into account:

1. Testability - not much of a difference. Both cases require code change to replace either the singleton itself or the "provided singleton"
2. Code Coupling - not much of a difference either (see comment on testability)
3. Scoping - Singletons most often live through the lifecycle of the whole application. It would be error prone to manage a singleton for some widget subtree. Here provider definitely has its strengths by taking care of creation and disposal.
4. UI updating - when using singletons this must be completely hand coded with setState which will produce lots of error prone boilerplate code. Provider provides this already under the hood.
5. Listeners - changing state in one part of the application should notify all consumers of that state. With singletons this has to be built by hand. Provider provides this already under the hood.
6. Lazy Loading - By default, values are lazy-loaded, which means they are called the first time the value is read instead of the first time the provider is created. This can be disabled by lazy: false

Hope this answers the question in more depth.