RxSwift+SJFluidSegmentedControl.swift

import UIKit
import RxSwift
import RxCocoa
import SJFluidSegmentedControl

func castOrThrow<T>(_ resultType: T.Type, _ object: Any) throws -> T {
    guard let returnValue = object as? T else {
        throw RxCocoaError.castingError(object: object, targetType: resultType)
    }
    return returnValue
}

private class RxSJFluidSegmentedControlDelegateProxy: DelegateProxy<SJFluidSegmentedControl, SJFluidSegmentedControlDelegate>,
    SJFluidSegmentedControlDelegate, DelegateProxyType {

    public weak private(set) var segmentControl: SJFluidSegmentedControl?

    public init(segmentControl: SJFluidSegmentedControl) {
        self.segmentControl = segmentControl
        super.init(parentObject: segmentControl, delegateProxy: RxSJFluidSegmentedControlDelegateProxy.self)
    }

    static func registerKnownImplementations() {
        self.register { RxSJFluidSegmentedControlDelegateProxy(segmentControl: $0) }
    }

    static func currentDelegate(for object: SJFluidSegmentedControl) -> SJFluidSegmentedControlDelegate? {
        return object.delegate as? SJFluidSegmentedControlDelegate
    }

    static func setCurrentDelegate(_ delegate: SJFluidSegmentedControlDelegate?, to object: SJFluidSegmentedControl) {
        let segmentControl: SJFluidSegmentedControl = object
        segmentControl.delegate = delegate
    }

}

extension Reactive where Base: SJFluidSegmentedControl {
    public var delegate: DelegateProxy<SJFluidSegmentedControl, SJFluidSegmentedControlDelegate> {
        return RxSJFluidSegmentedControlDelegateProxy.proxy(for: base)
    }

    public var toSegmentAtIndex: ControlEvent<Int> {

        let source = delegate
            .methodInvoked(
                #selector(
                    SJFluidSegmentedControlDelegate.segmentedControl(_:didChangeFromSegmentAtIndex:toSegmentAtIndex:)
                )
            )
            .map { segment in
                return try castOrThrow(Int.self, segment[2])
            }

        return ControlEvent(events: source)
    }

}