ReactiveCocoa 4 UIKit Extensions

UIKitExtensions.swift

//
//  UIKitExtensions.swift
//  ReactiveForms
//
//  Created by Rhys Powell on 12/10/2015.
//  Copyright © 2015 Rhys Powell. All rights reserved.
//

import Foundation
import ReactiveCocoa

func lazyAssociatedProperty<T: AnyObject>(host: AnyObject,
    key: UnsafePointer<Void>, factory: ()->T) -> T {
        var associatedProperty = objc_getAssociatedObject(host, key) as? T
        
        if associatedProperty == nil {
            associatedProperty = factory()
            objc_setAssociatedObject(host, key, associatedProperty,
                .OBJC_ASSOCIATION_RETAIN)
        }
        return associatedProperty!
}

func lazyMutableProperty<T>(host: AnyObject, key: UnsafePointer<Void>,
    setter: T -> (), getter: () -> T) -> MutableProperty<T> {
        return lazyAssociatedProperty(host, key: key) {
            let property = MutableProperty<T>(getter())
            property.producer
                .startWithNext { setter($0) }
            return property
        }
}

struct AssociationKey {
    static var hidden: UInt8 = 1
    static var alpha: UInt8 = 2
    static var text: UInt8 = 3
    static var enabled: UInt8 = 4
    static var action: UInt8 = 5
}

extension UIView {
    public var rac_hidden: MutableProperty<Bool> {
        return lazyMutableProperty(self, key: &AssociationKey.hidden, setter: { self.hidden = $0 }, getter: { return self.hidden })
    }
    
    public var rac_alpha: MutableProperty<CGFloat> {
        return lazyMutableProperty(self, key: &AssociationKey.alpha, setter: { self.alpha = $0 }, getter: { return self.alpha })
    }
}

extension UITextField {
    public var rac_text: MutableProperty<String> {
        return lazyAssociatedProperty(self, key: &AssociationKey.text) {
            
            self.addTarget(self, action: "rac_textChanged", forControlEvents: UIControlEvents.EditingChanged)
            
            let property = MutableProperty<String>(self.text ?? "")
            property.producer.startWithNext { self.text = $0 }
            return property
        }
    }
    
    func rac_textChanged() {
        rac_text.value = self.text ?? ""
    }
}


extension UIControl {
    var rac_enabled: MutableProperty<Bool> {
        return lazyMutableProperty(self, key: &AssociationKey.enabled, setter: { self.enabled = $0 }, getter: { return self.enabled })
    }
}

extension UIButton {
    var rac_action: Action<AnyObject?, Void, NoError>? {
        get {
            return objc_getAssociatedObject(self, &AssociationKey.action) as? Action<AnyObject?, Void, NoError>
        }
        set(action) {
            // Unbind old action
            if let oldAction = self.rac_action {
                self.removeTarget(oldAction.unsafeCocoaAction, action: CocoaAction.selector, forControlEvents: .TouchUpInside)
            }
            
            // Store and bind new action
            objc_setAssociatedObject(self, &AssociationKey.action, action, .OBJC_ASSOCIATION_RETAIN)
            if let action = action {
                self.rac_enabled <~ action.enabled
                self.addTarget(action.unsafeCocoaAction, action: CocoaAction.selector, forControlEvents: .TouchUpInside)
            }
        }
    }
}