How to use BehaviorRelay as an alternate to Variable in RxSwift?

Question

As of RxSwift4, Variable is moved to Deprecated.swift marking the possible deprecation of Variable in future. An alternate proposed to

Answer 1

AshKan answer is great but I came here looking for a missing method from the solution. Append:

extension BehaviorRelay where Element: RangeReplaceableCollection {
        
    func append(_ subElement: Element.Element) {
        var newValue = value
        newValue.append(subElement)
        accept(newValue)
    }
}

Answer 2

How about this kind of extension:

extension BehaviorRelay {

    var val: Element {
        get { value }
        set { accept(newValue) }
    }
}

Then use it as you were using the Variable, but instead of calling value, call val:

myFilter.val.append(newModel)

Answer 3

I would do something like that -

let requests = PublishSubject<Observable<ServerResponse>>.create()
let responses: Observable<ServerResponse> = requests.switchLatest()

let parsed: Observable<[ParsedItem]> = responses
  .flatMap { Observable.from($0).map { parse($0) }.toArray() }

parsed.bind(to: ui)

// repeated part
let request1: Observable<ServerResponse> = servive.call()
request.onNext(request1)

Answer 4

I created those this extension, with two methods to facilitate migration in case you have a Variable of Array and you have to use append.

    extension BehaviorRelay where Element: RangeReplaceableCollection {

        func append(_ subElement: Element.Element) {
            var newValue = value
            newValue.append(subElement)
            accept(newValue)
        }

        func append(contentsOf: [Element.Element]) {
            var newValue = value
            newValue.append(contentsOf: contentsOf)
            accept(newValue)
        }

        public func remove(at index: Element.Index) {
            var newValue = value
            newValue.remove(at: index)
            accept(newValue)
        }

        public func removeAll() {
            var newValue = value
            newValue.removeAll()
            accept(newValue)
        }

    }

and you call it like this

    var things = BehaviorRelay<[String]>(value: [])
    things.append("aa")
    let otherThings = ["bb", "cc"]
    things.append(contentsOf: otherThings) 
    things.remove(at: 0)
    things.removeAll()

Answer 5

On Variable used to have:

let variable = Variable("Hello RxSwift")
variable.value = "Change text" 
print(variable.value) // "Change text"

On BehaviorRelay you have to use:

let relay = BehaviorRelay(value: "Hello RxSwift")
relay.accept("Change text")
print(relay.value) // "Change text"

Answer 6

Have you considered simply creating a new array from the existing value on the relay, appending, then calling accept?

myFilter.accept(myFilter.value + [newModel])