Reswift: How to filter state???

[luongnhatlam]

I have a question?? How to filter the state what I only want to select it to my viewmodel (viewcontroller) need to use? API and syntax in ReSwift sometimes change, so I used old syntax cause error. Please help me

[DivineDominion]

From http://reswift.github.io/ReSwift/master/getting-started-guide.html:

    // we are only interested in repository substate, filter it out of the overall state
    store.subscribe(self) { subcription in
        subcription.select { state in state.repositories }
    }

Does that work for you?

[luongnhatlam]

Thanks for your response but it don't work for me

[nikans]

https://github.com/ReSwift/ReSwift/releases

Subselecting state in 4.0.0:

store.subscribe(subscriber) {
  $0.select {
    ($0.testValue, $0.otherState?.name)
  }
}

But actually the tuple doesn't work for me, only single substate like that:

store.subscribe(subscriber) {
  $0.select {
    $0.otherState
  }
}

You should also define types in newState(state:) method

func newState(state: SomeState) {
    ...
}

[luongnhatlam]

Type of expression is ambiguous without more context
when I insert the single substate:

store.subscribe(subscriber) {
  $0.select {
    $0.otherState
  }
}

[DivineDominion]

Try to add type annotations first. Then the error will be more precise. This is probalby because subscriber's newState method parameter does not match whatever otherState is.

[luongnhatlam]

@DivineDominion Sorry, I do not understand

[DivineDominion]

Instead of the enumerated closure parameters ($0, $1, ...), add explicit types, as in:

$0.select { (state: AppState) -> SomeSubState in
    state.otherState
 }

[luongnhatlam]

The error is Cannot invoke 'select' with an argument list of type '((AppState) -> SomeSubState)

[luongnhatlam]

Ok thank all, I fixed it, so I have more a question, each ViewModel always subscribe to Store and conform StoreSubscriber protocol, is there a way to write code one time??

[DivineDominion]

Cool! What was the fix?

You cannot bypass implementing the subscriber protocol. You can get rid of some ceremony if you use a reactive library like RxSwift where code exists which lets you write closure subscriptions instead of dedicated objects. Thinking about it, maybe open a new "enhancement" issue where you suggest a closure-based extension without you having to write types that conform to StoreSubscriber.

[luongnhatlam]

The fix was simple! I have some ViewModel and a BaseViewModel, ViewModels is inheritance of BaseVM, BaseVM adopt to StoreSubscriber protocol, so my VMs only override the newState method. Now I fix it by adopting StoreSubscriber pers VM, so I can receive the State I want and select closure will be explicit

[luongnhatlam]

But I have a problem. I want to skip when value of state is equal, I must adopt Equatable for my State but when run app, it will be crash. The code like this:
extension EventHomeState:Equatable {
static func ==(lhs: EventHomeState, rhs: EventHomeState) -> Bool {
return lhs == rhs
}
}

[DivineDominion]

Sure, this is a recursion. You need to compare the individual values of both EventHomeStates, lhs and rhs. See: http://nshipster.com/swift-comparison-protocols/

[luongnhatlam]

Thank guys, you are so kind. If then I have any problem, hope you also to help me.

[DivineDominion]

You're welcome!