Changing one property in a variable triggers subcriptions to other properties. RxSwift - ios

Question

I have the following struct of properties for Chat
struct Chat {
var id = String()
var gender = String()
var date = Date()
init() {}
}
In a view controller, i declare an instance of Chat called observablechat, and then i used the flatmap operator to attempt and observe only changes in the date property of observablechat. However, if i change the gender property (as shown), the subscription gets triggered. I wonder why that is and how can i fix this code such that the subscription only looks at what happens to the date property and nothing else?
class ViewController: UIViewController {
var observablechat = Variable(Chat())
observablechat.asObservable()
.flatMap { (Chat) -> Observable<Date> in
return Observable.of(Chat.matchDate)
}.subscribe(onNext: { (r) in
print(r)
}).addDisposableTo(disposeBag)
self.observablechat.value.gender = "male"
//triggers subscription above.
}
}

Answer 1

First of all, why flatMap?
You need only distinctUntilChanged and map. DebugPrint will be triggered only twice: initial setup + date changed once. Check out the code below and feel free to ask questions.
import PlaygroundSupport
import RxSwift
struct Chat {
var id: String
var gender: String
var date: Date
init(id: String = "", gender: String = "", date: Date = Date(timeIntervalSince1970: 0)) {
self.id = id
self.gender = gender
self.date = date
}
}
final class YourClass {
lazy var variableChat: Variable<Chat> = Variable<Chat>(Chat())
var observableDate: Observable<Date> {
return variableChat
.asObservable()
.distinctUntilChanged({ (chatOld, chatNew) -> Bool in
return chatOld.date == chatNew.date
})
.map({ (chat) -> Date in
return chat.date
})
.shareReplay(1)
}
}
let value = YourClass()
value.observableDate
.subscribe(onNext: { (date) in
debugPrint(date.timeIntervalSince1970)
})
value.variableChat.value.gender = "male"
value.variableChat.value.date = Date()
value.variableChat.value.gender = "female"
value.variableChat.value.gender = "male"
value.variableChat.value.gender = "female"
P.S. the way to run RxSwift in playground: readme