Question 68862 in IOS Swift Question posted in
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iOS – MVVM Data Binding – Ios swift

I am working with MVVM design architecture, I have gone through multiple articles about data binding. We can achieve data binding through Protocol, Closure, and Third Party(like RxSwift).
So, if I am wrong please correct me otherwise let me know "how many ways to bind the data in iOS(Swift) MVVM design architecture?"

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2

Answers


  1. 0

    The easiest one is by using Observable class binding known as Boxing.
    create an Observable class:

    class Observable<T> {

var value: T? {
    didSet {
        DispatchQueue.main.async {
            self.listener?(self.value)
        }
    }
}

init( _ value: T?) {
    self.value = value
}

private var listener: ((T?) -> Void)?

func bind(_ listener: @escaping (T?) -> Void) {
    listener(value)
    self.listener = listener
}
}

    in your viewModel define it in this way:
    (this is a sample for showing loader in your view controller)

    var isLoadingData: Observable<Bool> = Observable(false)

    Because the Observable class is a generic type, you can pass other types to it.

    in your view model you can set the value:

    isLoadingData.value = true

    then in your view controller use something like this:

       viewModel.isLoadingData.bind { [weak self] loading in
        guard let loading = loading, let self = self else {
            return
        }
        DispatchQueue.main.async {
            if loading {
                //Show a loader
            } else {
                //Hide a loader
            }
        }
    }

    As soon as a value is assigned to the isLoadingData object, it will trigger your view controller. We have to use [Weak self] to avoid strong references.

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  2. 0

    Due to I need multiple observer and I don’t want the closure still exist when the ViewController is gone.
    I make some changes from Sajjad Sarkoobi code.

    typealias ListenerClosure = @convention(block) (_ T: AnyObject?) -> ()

class Observable<T: AnyObject> {

    var value: T? {
    
        didSet {
        
            self.listeners.forEach({ unsafeBitCast($0, to: ListenerClosure.self)(value) })
        
        }
    
    }

    private var listeners: [AnyObject] = []

    init(_ value: T?) {
    
        self.value = value
    
    }

    func bind(_ listener: @escaping ListenerClosure) {
    
        listener(value)
    
        let anyObject = unsafeBitCast(listener, to: AnyObject.self)
    
        self.listeners.append(anyObject)
    
    }

    func unbind(_ listener: @escaping ListenerClosure) {

        let anyObject = unsafeBitCast(listener, to: AnyObject.self)
            
        self.listeners.removeAll(where: { $0 === anyObject })
    
    }

}

    in your viewModel define it in this way

    var currentUUID: Observable<NSUUID> = Observable(nil)

    Set the value in ViewModel

    self.currentUUID.value = NSUUID()

    Use bind and unbind in your ViewController. I want the closure removed from Observable listeners array, so I unbind it when viewController deinit.

    The capture list [weak self] is required if use self
    reference in closure or this viewController will not deinit.

    class ViewController: NSViewController {

    var viewModel: ViewModel?

    private var listener: ListenerClosure!

    override func viewDidLoad() {
        super.viewDidLoad()
    
        self.listener = { [weak self] uuid in
            
            //self?.doSomething()

            print("observed ViewModel currentUUID (uuid)")
        
        }
    
        self.viewModel?.currentUUID.bind(self.listener)
    }

    deinit {
    
        print("ViewController deinit")
    
        self.viewModel?.currentUUID.unbind(self.listener)
    }
}
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