lesson4.1_reachability

Lesson 4.1: ReachabilityService

Problem statement

Write an app which uses view.backgroundColor to reflect the state of network reachability:

• greenColor when reachable
• redColor when not reachable

Problem project

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

I have added a dependency against Reachability.swift to the Cartfile, and I have pulled in a copy of ReachabilityService.swift from RxExample.

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

Discussion:

Here, we subscribe to the ReachabilityService from RxExample and set the background color accordingly:

ViewController.swift:

import UIKit
import RxSwift
import RxCocoa

class ViewController: UIViewController {

    private let disposeBag = DisposeBag()
    
    override func viewDidLoad() {
        super.viewDidLoad()
        
        ReachabilityService.sharedReachabilityService.reachabilityChanged.subscribeNext { [weak self] (status) -> Void in
            switch status
            {
            case .Reachable:
                self?.view.backgroundColor = UIColor.greenColor()
            case .Unreachable:
                self?.view.backgroundColor = UIColor.redColor()
            }
        }.addDisposableTo(disposeBag)
    }
}

However, our closure is both converting a ReachabilityStatus into a UIColor, and applying that color to view.backgroundColor. We can separate these two concerns by using the map function:

import UIKit
import RxSwift
import RxCocoa

class ViewController: UIViewController {

    private let disposeBag = DisposeBag()
    
    override func viewDidLoad() {
        super.viewDidLoad()
        
        ReachabilityService.sharedReachabilityService.reachabilityChanged.map { (status) -> UIColor in
            switch status
            {
            case .Reachable:
                return UIColor.greenColor()
            case .Unreachable:
                return UIColor.redColor()
            }
        }.subscribeNext { [weak self] (color) -> Void in
            self?.view.backgroundColor = color
        }.addDisposableTo(disposeBag)
    }
}

Start up the app in the simulator, then toggle your Mac's wifi on and off and verify the background color changes to reflect this.

However, there is a problem with this solution:

• When the app first starts up, it doesn't recieve an Event from ReachabilityService to reflect the initial ReachabilityStatus. That is, view.backgroundColor is white until a change in ReachabilityStatus occurs. We will address this in Lesson 4.2.

New concepts to explore

• Read through ReachabilityService.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.