CombineViewModel

CombineViewModel is Swift Combine version of RDXVM.

Note: More validations are needed.

Example

To run the example project, clone the repo, and run pod install from the Example directory first.

Requirements

• Swift 5
• iOS 13

Installation

CombineViewModel is available through CocoaPods. To install it, simply add the following line to your Podfile:

pod 'CombineViewModel'

Usage

ViewModel needs custom types for action, mutation, event, and state to subclass and create an instance.

enum Action {
    case add(Int)
    case subtract(Int)
}
enum Mutation {
    case add(Int)
    case calculating(Bool)
}
enum Event {
    case notSupported
}
struct State {
    var sum = 0
    var calculating = false
}

You can subclass ViewModel with these types and must override react(action:state:) and reduce(mutation:state:) methods. In react(action:state:, you should return an observable of Reaction:

• a mutation to mutate state as the result of an action
• an event to notify some event to view
• an error that is explicit/implicit thrown
• an action that is mapped from another action.

class CalcViewModel: ViewModel<Action, Mutation, State, Event> {
    init(state: State = State()) {
        super.init(state: state)
    }

    override func react(action: Action, state: State) -> Observable<Reaction> {
        switch action {
        case .add(let num):
            return .of(.mutation(.calculating(true)),
                .mutation(.add(num)),
                .mutation(.calculating(false)))
        case .subtract:
            return .just(.event(.notSupported))
        }
    }

    override func reduce(mutation: Mutation, state: State) -> State {
        var state = state
        switch mutation {
        case let .add(let num):
            state.sum += num
        case let .calculating(let calculating):
            state.calculating = calculating
        }
        return state
    }
}

let vm = CalcViewModel<Action, Mutation, Event, State>()

Send actions to ViewModel and get outputs(event, error, state) from ViewModel.

addButton.rx.tap.map { Action.add(3) }
    .bind(to: vm.action)
    .disposed(by: dbag)

vm.event
    .emit()
    .disposed(by: dbag)

vm.error
    .emit()
    .disposed(by: dbag)

vm.state
    .drive()
    .disposed(by: dbag)

You can get current value of the state or property of the state.

// current state itself
vm.$state

// current value of state's property
vm.$state.sum

You can apply the @Drived attribute to a property of state, so you can directly drive that property instead of the state itself.

struct State {
    @Drived var sum = 0
    @Drived var calculating = false
}

vm.$state.$sum.drive()
vm.$state.$calculating.drive()

Author

skyofdwarf, [email protected]

License

CombineViewModel is available under the MIT license. See the LICENSE file for more info.