Using PublishSubject

UIImagePickerController.swift

//
//  ViewController.swift
//  RxSubject
//
//  Created by Hung Dinh Van on 12/27/16.
//  Copyright © 2016 ChuCuoi. All rights reserved.
//

import UIKit
import RxSwift
import RxCocoa

class ViewController: UIViewController {
    override func viewDidLoad() {
        super.viewDidLoad()
        
        let imagePicker = UIImagePickerController()
        imagePicker.delegate = self
        
        button.rx.tap.subscribe(onNext: { [unowned self] in
            imagePicker.allowsEditing = false
            imagePicker.sourceType = .photoLibrary
            self.present(imagePicker, animated: true, completion: nil)
        }).addDisposableTo(disposeBag)
        
        didFinishPickingSubject.subscribe(onNext: { [unowned self] info in
            if let pickedImage = info[UIImagePickerControllerOriginalImage] as? UIImage {
                self.imageView.contentMode = .scaleAspectFit
                self.imageView.image = pickedImage
            }
            self.dismiss(animated: true, completion: nil)
        }).addDisposableTo(disposeBag)
    }
    
    @IBOutlet fileprivate weak var imageView: UIImageView!
    @IBOutlet fileprivate weak var button: UIButton!
    
    fileprivate let disposeBag = DisposeBag()
    fileprivate let didFinishPickingSubject = PublishSubject<[String : Any]>()
}

extension ViewController: UIImagePickerControllerDelegate, UINavigationControllerDelegate {
    func imagePickerController(_ picker: UIImagePickerController, didFinishPickingMediaWithInfo info: [String : Any]) {
        didFinishPickingSubject.onNext(info)
    }
}