HasDisposeBag.swift

//
//  DisposeBagable.swift
//  NSObject-Rx
//
//  Created by Thibault Wittemberg on 2017-08-25.
//  Copyright © 2017 RxSwiftCommunity. All rights reserved.
//

import Foundation
import RxSwift
import ObjectiveC

fileprivate struct AssociatedKeys {
    static var disposeBag = "disposeBag"
}

/// each DisposeBagable offers a unique Rx DisposeBag instance
public protocol HasDisposeBag {

    /// a unique Rx DisposeBag instance
    var disposeBag: DisposeBag { get set }
}

extension HasDisposeBag {

    private func doLocked(forClosure closure: () -> Void) {
        objc_sync_enter(self); defer { objc_sync_exit(self) }
        closure()
    }

    public var disposeBag: DisposeBag {
        get {
            var rxDisposeBag: DisposeBag!
            doLocked {
                let lookup = objc_getAssociatedObject(self, &AssociatedKeys.disposeBag) as? DisposeBag
                if let lookup = lookup {
                    rxDisposeBag = lookup
                } else {
                    let newDisposeBag = DisposeBag()
                    objc_setAssociatedObject(self, &AssociatedKeys.disposeBag, newDisposeBag, .OBJC_ASSOCIATION_RETAIN_NONATOMIC)
                    rxDisposeBag = newDisposeBag
                }
            }
            return rxDisposeBag
        }

        set {
            doLocked {
                objc_setAssociatedObject(self, &AssociatedKeys.disposeBag, newValue, .OBJC_ASSOCIATION_RETAIN_NONATOMIC)
            }
        }
    }
}