lesson2.3_map

Lesson 2.3: map

Problem statement

Modify RxSwiftButtonBackgroundColorDemo to use the map function to transform the Event sent by rx_tap into a UIColor which by applied by the closure passed to func subscribeNext.

Problem project

You can use the project in the problem folder of this repo as a starting point.

Note: I have omitted the Carthage folder from the problem project, because it includes large binary files. In order to use the this project, you will need to run carthage update --platform iOS.

Solution

ViewController.swift:

import UIKit
import RxSwift
import RxCocoa

class ViewController: UIViewController {

    @IBOutlet weak var button: UIButton!
    
    var disposeBag = DisposeBag()
    
    override func viewDidLoad() {
        super.viewDidLoad()
        
        button.rx_tap.map { () -> UIColor in
            
            return UIColor.greenColor()
            
        }.subscribeNext { [weak self] (color) -> Void in
            
            self?.view.backgroundColor = color
            
        }.addDisposableTo(disposeBag)
        
    }
}

Discussion:

We introduce the map function and use it to transforms a Void into a UIColor. This allows us to make the closure which we pass to subscribeNext accept any UIColor, rather than being hard-coded to always use greenColor.

New concepts to explore

• Open up RxExample.xcodeproj.
  • Take a look at func map in Observable+StandardSequenceOperators.swift
  • Take a look at func composeMap in Observable.swift
  • Take a look at class Map in Map.swift

Solution project

My solution is included in the solution folder of this repo.

Note: I have omitted the Carthage folder from the solution project, because it includes large binary files. In order to run the this project, you will need to run carthage update --platform iOS.