RxSwift subscribe will work when initiated

Question

I am using RxSwift for the first time. It will load Post List from my server. The first time only need to run loadPostList but Just by initializing the model, nextPage is called.

Please let me know what I'm doing wrong.

class PostNetworkModel {
    var nextPage:BehaviorSubject<Void> = BehaviorSubject(value: ())
    var reFresh:BehaviorSubject<Void> = BehaviorSubject(value: ())
    var raiseError:BehaviorSubject<Void> = BehaviorSubject(value: ())
    var isLoadingComplete = false
    private var pageNo = BehaviorRelay(value: 1)
    var postList : BehaviorRelay<[Post]> = BehaviorRelay(value: [])
    let disposeBag = DisposeBag()
    init() {
        loadPostList()
            .bind(to: postList)
            .disposed(by: disposeBag)

        postList
            .asObservable()
            .subscribe({ ( _) in
                self.isLoadingComplete = true
            })
            .disposed(by: disposeBag)

        nextPage
            .asObservable()
            .subscribe(onNext: { [weak self] ( _) in
                print("nextPage")
                if (self?.isLoadingComplete)!{
                    self?.isLoadingComplete = false
                    self?.pageNo.accept(self!.pageNo.value + 1)
                }
            })
            .disposed(by: disposeBag)
     }
}

Answer 1

BehaviorSubject accepts an initial value as constructor parameter because its specification is as follows:

Observers can subscribe to the subject to receive the last (or initial) value and all subsequent notifications.

Meaning nextPage will trigger a next even on subscription. You'll probably want to change all the BehaviorSuject to PublishSubject for this class

class PostNetworkModel {
    var nextPage:PublishSubject<Void> = PublishSubject()
    var reFresh:PublishSubject<Void> = PublishSubject()
    var raiseError:PublishSubject<Void> = PublishSubject()
    var isLoadingComplete = false
    private var pageNo = BehaviorRelay(value: 1)
    var postList : PublishRelay<[Post]> = PublishRelay()

    let disposeBag = DisposeBag()
    init() {
        loadPostList()
            .bind(to: postList)
            .disposed(by: disposeBag)

        postList
            .asObservable()
            .subscribe({ ( _) in
                self.isLoadingComplete = true
            })
            .disposed(by: disposeBag)

        nextPage
            .asObservable()
            .subscribe(onNext: { [weak self] ( _) in
                print("nextPage")
                if (self?.isLoadingComplete)!{
                    self?.isLoadingComplete = false
                    self?.pageNo.accept(self!.pageNo.value + 1)
                }
            })
            .disposed(by: disposeBag)
     }
}

Note than I kept pageNo as a BehaviorRelay , as it makes sense for this observable to have an initial value.