Feature Request: Make the entire store readonly

[AlaaEldeenYsr]

Our project structure depends on immutable state management. All the mobx stores in the project should be immutable, All the observables in the mobx stores should be mutated only from inside the stores, In that case I give readonly annotation for every single observable, I think it would be more much easy if we give only one readonly annotation for the store to make all the observables inside immutable without giving the annotation for every single observable.

[Ascenio]

Sounds nice, but there's a catch. What if the class has private dependencies which it doesn't want to expose? There should be a way to avoid generating getters for them.

[benfgit]

One approach could be, if a public variable is annotated with @observable in a @readonly store, then it will be exposed to outside. If the variable is private, it will be available for in-store use only. When you add this to the current @readonly solution, it might be confusing. Developers should know about what happens when:

• @observable is used on a public variable in a read-write store
• @observable is used on a private variable in a read-write store
• @observable is used on a public variable in a read-only store.
• @observable is used on a private variable in a read-only store.
• @readonly is used on a public variable in a read-write store.
• @readonly is used on a private variable in a read-write store.

When Mobx stores considered as state objects for Flutter apps, observable's should not be mutated directly. Default behaviour should be read-only and mutations should be perfromed by action's.

When stores are read-only by default (and @readonly is deprecated), the total cases will be reduced to a fair amount. Only exception will be to make an observable read-write outside of the store. That could be handled by an exceptional annotation such as @observable(readonly: false). When this applied, 3 possibilities occurs:

• @observable is used on a public variable (It will be read-only outside of the store)
• @observable is used on a private variable (It will be hidden to outside, in-store use only)
• @observable(readonly: false) is used on a public variable (It will be read-write outside of the store. This will be very exceptional since recommended way is to mutate the state via actions but developer still have the option to not to.)

Current codegen supports mutability and treats immutability as exception. It needs to be reversed and immutability should be imposed by codegen, docs and examples.

[Ascenio]

I do think readonly should be the default behavior, but that would break so much code. That would be a breaking change similar to bloc's latest changes. In similar way, we could setup a issue for discussion and see if people agree with the changes before anything else.

If we don't come to do that, I like the idea of using @readonly in the store and annotate public fields with @observer, which in most cases should be no or few fields. What do you think @pavanpodila?

[benfgit]

I agree. We should discuss it further and it will be a breaking change.

@observable should be equivalent to Stream<T>. It should be open for subscription but closed for mutation. Right now it's more likely equivalent of StreamController<T>.