Class adding a support for observing a property.

Observable.swift

final class Observable<T> {
    init(_ value: T) {
        self.value = value
    }
    
    var value: T {
        didSet {
            changeHandlers.forEach({ $0.handler(value) })
        }
    }
    
    typealias ChangeHandler = ((T) -> Void)
    private var changeHandlers: [(identifier: Int, handler: ChangeHandler)] = []
    
    /**
     Adds observer to the value.
     - parameter initial: The handler is run immediately with initial value.
     - parameter handler: The handler to execute when value changes.
     - returns: Identifier of the observer.
     */
    @discardableResult func observe(initial: Bool = false, handler: @escaping ChangeHandler) -> Int {
        let identifier = UUID().uuidString.hashValue
        changeHandlers.append((identifier, handler))
        guard initial else { return identifier }
        handler(value)
        return identifier
    }
    
    /**
     Removes observer to the value.
     - parameter observer: The observer to remove.
     */
    func removeObserver(_ observer: Int) {
        changeHandlers = changeHandlers.filter({ $0.identifier != observer })
    }
}