FireBoltt_ios/FireBoltt/Extensions/UIImagePickerController+Rx.swift

//
//  UIImagePickerController+Rx.swift
//  RxExample
//
//  Created by Segii Shulga on 1/4/16.
//  Copyright © 2016 Krunoslav Zaher. All rights reserved.
//


import RxSwift
import RxCocoa
import UIKit

//图片选择控制器（UIImagePickerController）的Rx扩展
extension Reactive where Base: UIImagePickerController {
    
    //代理委托
    public var pickerDelegate: DelegateProxy<UIImagePickerController,
        UIImagePickerControllerDelegate & UINavigationControllerDelegate > {
        return RxImagePickerDelegateProxy.proxy(for: base)
    }
    
    //图片选择完毕代理方法的封装
    public var didFinishPickingMediaWithInfo: Observable<[String : AnyObject]> {
        
        return pickerDelegate
            .methodInvoked(#selector(UIImagePickerControllerDelegate
                .imagePickerController(_:didFinishPickingMediaWithInfo:)))
            .map({ (a) in
                return try castOrThrow(Dictionary<String, AnyObject>.self, a[1])
            })
    }
    
    //图片取消选择代理方法的封装
    public var didCancel: Observable<()> {
        return pickerDelegate
            .methodInvoked(#selector(UIImagePickerControllerDelegate
                .imagePickerControllerDidCancel(_:)))
            .map {_ in () }
    }
}

//转类型的函数（转换失败后，会发出Error）
fileprivate 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
}