How to pass data from delegate method to the observable's onNext method in RxSwift?

Question

I have manager class which will connect and manage the data and state of the Bluetooth device.

The manager class conforms to IWDeviceManagerDelegate and has a method which gives the weight data func onReceiveWeightData(_ device: IWDevice!, data: IWWeightData!).

Once I call listenToWeight() from any controller I want to give the data using Observable.

How I fire an onNext event with the data of onReceiveWeightData method to listenToWeight observable?

Below is the code.

class WeightMachineManager: NSObject {

    func setup() {
        IWDeviceManager.shared()?.delegate = self
        IWDeviceManager.shared()?.initMgr()
    }

    func listenToWeight() -> Observable<IWWeightData> {
        let tag = WeightMachineManager.tag
        if let connectedDevice = connectedDevice {
            IWDeviceManager.shared()?.add(connectedDevice, callback: { (device, code) in
                if code == .success {
                    print("\(tag)[SUCCESS] Device added successfully.")
                } else {
                    print("\(tag)[FAILURE] Failed to add device.")
                }
            })
        } else {
            print("\(tag)[FAILURE] Couldn't find any device to connect.")
        }
    }
}

extension WeightMachineManager: IWDeviceManagerDelegate {
    func onReceiveWeightData(_ device: IWDevice!, data: IWWeightData!) {
        // TODO:- Pass this data in the onNext event of listenToWeight's observable.
    }
}

What is an `ICDeviceManager`? What is a `IWDeviceManagerDelegate`? Are they related to each other in some way? Your `listenToWeight()` never returns anything. — Daniel T., Sep 22 '19 at 16:15
@DanielT. Yes they are related to each other. `IWDeviceManager` a manager who connects to the hardware. `IWDeviceManagerDelegate` is the protocol. This protocol has the method which returns the weight data. I don't know what to return in `listenToWeight()` method as there I am only assigning the device which has to measure the weight. The devices sdk returns weight in the `IWDeviceManagerDelegate's` method. — Anirudha Mahale, Sep 22 '19 at 16:28
The answer can be found here: https://stackoverflow.com/questions/51816144/how-to-convert-delegate-to-observable-rxswift/51824142#51824142 — Daniel T., Sep 22 '19 at 16:29
Thanks for the post, If you don't mind can you show me this in my code — Anirudha Mahale, Sep 22 '19 at 16:31

score 1 · Accepted Answer · answered Sep 22 '19 at 17:00

I've made a lot of assumptions in the below, but the result should look something like this:

class WeightMachineManager {

    var connectedDevice: IWDevice?

    func setup() {
        IWDeviceManager.shared()?.initMgr()
    }

    func listenToWeight() -> Observable<IWWeightData> {
        if let connectedDevice = connectedDevice, let deviceManager = IWDeviceManager.shared() {
            return deviceManager.rx.add(connectedDevice)
                .flatMap { deviceManager.rx.receivedWeightData() } // maybe this should be flatMapLatest or flatMapFirst. It depends on what is calling listenToWeight() and when.
        }
        else {
            return .error(NSError.init(domain: "WeightMachineManager", code: -1, userInfo: nil))
        }
    }
}

extension IWDeviceManager: HasDelegate {
    public typealias Delegate = IWDeviceManagerDelegate
}

class IWDeviceManagerDelegateProxy
    : DelegateProxy<IWDeviceManager, IWDeviceManagerDelegate>
    , DelegateProxyType
    , IWDeviceManagerDelegate {

    init(parentObject: IWDeviceManager) {
        super.init(parentObject: parentObject, delegateProxy: IWDeviceManagerDelegateProxy.self)
    }

    public static func registerKnownImplementations() {
        self.register { IWDeviceManagerDelegateProxy(parentObject: $0) }
    }
}

extension Reactive where Base: IWDeviceManager {

    var delegate: IWDeviceManagerDelegateProxy {
        return IWDeviceManagerDelegateProxy.proxy(for: base)
    }

    func add(_ device: IWDevice) -> Observable<Void> {
        return Observable.create { observer in
            self.base.add(device, callback: { device, code in
                if code == .success {
                    observer.onNext(())
                    observer.onCompleted()
                }
                else {
                    observer.onError(NSError.init(domain: "IWDeviceManager", code: -1, userInfo: nil))
                }
            })
            return Disposables.create()
        }
    }

    func receivedWeightData() -> Observable<IWWeightData> {
        return delegate.methodInvoked(#selector(IWDeviceManagerDelegate.onReceiveWeightData(_:data:)))
            .map { $0[1] as! IWWeightData }
    }
}

`extension IWDeviceManager: HasDelegate` asks to add `var delegate: Delegate? { get set }` in there. I think you haven't added it there. — Anirudha Mahale, Sep 23 '19 at 15:10
In your question you called `.delegate = self`. That tells me that the var already exists. — Daniel T., Sep 23 '19 at 15:14
Yes you did: `IWDeviceManager.shared()?.delegate = self`. That said, to solve this, you will need to implement a `{ get set}` for delegate and get and set the delegate. — Daniel T., Sep 23 '19 at 15:17
Like this `public var delegate: IWDeviceManagerDelegate? { get { return IWDeviceManager.shared()?.delegate } set(newValue) { IWDeviceManager.shared()?.delegate = newValue } }` ????? — Anirudha Mahale, Sep 23 '19 at 15:18
It crashes while getting and setting the value. Any reason why or am not doing it correctly. — Anirudha Mahale, Sep 23 '19 at 16:36

How to pass data from delegate method to the observable's onNext method in RxSwift?

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