Swift - ReSwift Subscribe to multiple substates - swift

Question

i am using ReSwift in my project to get a nice and clean redux architecture.
As i am not interested in the whole state i just subscribe to two substates for my viewcontroller:
extension ViewController: StoreSubscriber {
override func viewWillAppear(_ animated: Bool) {
store.subscribe(self) {
$0.select {
($0.subStateA, $0.subStateB)
}
}
}
override func viewWillDisappear(_ animated: Bool) {
store.unsubscribe(self)
}
func newState(state: (subStateA: SubStateA, subStateB: SubStateB)) {
print("test")
}
}
What happens:
My newState method is called every time any update happens to the store.
For example if i update subStateC it still triggers
func newState(state: (subStateA: SubStateA, subStateB: SubStateB)) {}
Can anybody explain why this happens?
Thanks and Greetings!

Answer 1

You can use skipRepeats after select invocation.
This problem is when you need only update state if substate was changed, using skipRepeats you can put a check if this is true you will skip the update, look this code to try to understand.
Example Code
This is a simple code about a state with navigation state and we want update state when navigation state change.
store.subscribe(self) { (subscriber:Subscription<State>) -> Subscription<RoutingState> in
subscriber.select({ (state:State) -> RoutingState in
return state.routing;
}).skipRepeats({ (oldRoutingState, newRoutingState) -> Bool in
return oldRoutingState.navigationState == newRoutingState.navigationState
})
}
This code will prevent call newState if nothing change in your filter.
I hope was helpful

Answer 2

Just do not subscribe whole ViewController or your ViewModel to states.
You can make subclasses (for example DataProvider) - subscribers for each state you need.
ViewController: UIViewController {
let dataProviderA = DataProviderA()
let dataProviderB = DataProviderB()
func viewDidLoad() {
super.viewDidLoad()
store.subscribe(self.dataProviderA) { $0.select { state in state.subStateA }. skipRepeats() }
store.subscribe(self.dataProviderB) { $0.select { state in state.subStateB }. skipRepeats() }
}
}
and your dataProviders must be StoreSubscribers of course:
class DataProviderA: StoreSubsciber<SubStateA> {
func newState(state: SubStateA) {
handle(state)
}
}
class DataProviderB: StoreSubsciber<SubStateB> {
func newState(state: SubStateB) {
handle(state)
}
}
I trust this is right approach - each object handle single state. Cheers!