DEV Community: Shu

Gradient View in Swift

Shu — Mon, 02 Sep 2019 04:16:32 +0000

Will write a really simple way to make a gradient UIView. You can specify GradientView in Stroyboard, then you can modify the UI settings.


import UIKit

@IBDesignable
class GradientView: UIView {

    @IBInspectable var cornerRadius: Double {
        get {
            return Double(self.layer.cornerRadius)
        }set {
            self.layer.cornerRadius = CGFloat(newValue)
        }
    }
    @IBInspectable var borderWidth: Double {
        get {
            return Double(self.layer.borderWidth)
        }
        set {
            self.layer.borderWidth = CGFloat(newValue)
        }
    }
    @IBInspectable var borderColor: UIColor? {
        get {
            return UIColor(cgColor: self.layer.borderColor!)
        }
        set {
            self.layer.borderColor = newValue?.cgColor
        }
    }
    @IBInspectable var shadowColor: UIColor? {
        get {
            return UIColor(cgColor: self.layer.shadowColor!)
        }
        set {
            self.layer.shadowColor = newValue?.cgColor
        }
    }
    @IBInspectable var shadowOpacity: Float {
        get {
            return self.layer.shadowOpacity
        }
        set {
            self.layer.shadowOpacity = newValue
        }
    }

    @IBInspectable var startColor:   UIColor = UIColor.black { didSet { updateColors() }}
    @IBInspectable var endColor:     UIColor = UIColor.white { didSet { updateColors() }}
    @IBInspectable var startLocation: Double =   0.05 { didSet { updateLocations() }}
    @IBInspectable var endLocation:   Double =   0.95 { didSet { updateLocations() }}
    @IBInspectable var horizontalMode:  Bool =  false { didSet { updatePoints() }}
    @IBInspectable var diagonalMode:    Bool =  false { didSet { updatePoints() }}

    override public class var layerClass: AnyClass { return CAGradientLayer.self }

    var gradientLayer: CAGradientLayer { return layer as! CAGradientLayer }

    func updatePoints() {
        if horizontalMode {
            gradientLayer.startPoint = diagonalMode ? CGPoint(x: 1, y: 0) : CGPoint(x: 0, y: 0.5)
            gradientLayer.endPoint   = diagonalMode ? CGPoint(x: 0, y: 1) : CGPoint(x: 1, y: 0.5)
        } else {
            gradientLayer.startPoint = diagonalMode ? CGPoint(x: 0, y: 0) : CGPoint(x: 0.5, y: 0)
            gradientLayer.endPoint   = diagonalMode ? CGPoint(x: 1, y: 1) : CGPoint(x: 0.5, y: 1)
        }
    }
    func updateLocations() {
        gradientLayer.locations = [startLocation as NSNumber, endLocation as NSNumber]
    }
    func updateColors() {
        gradientLayer.colors    = [startColor.cgColor, endColor.cgColor]
    }

    override public func layoutSubviews() {
        super.layoutSubviews()
        updatePoints()
        updateLocations()
        updateColors()
    }
}

How to use Error protocol easily in Swift

Shu — Mon, 12 Aug 2019 09:12:42 +0000

Swift has Error protocol that does not have anything default. iOS developers have to extend this protocol to deal with errors in their app. I will introduce a very simple example to manage custom errors. You can define your error cases like following.

// Error+Extension.swift

enum CustomError: Error {
    case errorOne
    case errorTwo
    case errorThree(message: String)
}

extension CustomError: LocalizedError {
    var errorDescription: String? {
        switch self {
        case .errorOne:
            return NSLocalizedString("Error one's description", comment: "Custom Error")
        case .errorTwo:
            return NSLocalizedString("Error two's description", comment: "Custom Error")
        case .errorThree(let message):
            return NSLocalizedString(message, comment: "Custom Error")
        }
    }
}

I wrote an article about handling UIAlertController. Using this AlertController, Error+Extension.swift can be improved like this.

// Error+Extension.swift
enum CustomError: Error {
    case errorOne
    case errorTwo
    case errorThree(message: String)
}

extension CustomError: LocalizedError {
    var errorDescription: String? {
        switch self {
        case .errorOne:
            return NSLocalizedString("Error one's description", comment: "Custom Error")
        case .errorTwo:
            return NSLocalizedString("Error two's description", comment: "Custom Error")
        case .errorThree(let message):
            return NSLocalizedString(message, comment: "Custom Error")
        }
    }
}

extension Error {
    func displayAlert(completion: (() -> Void)? = nil) {
        let alert = AlertController(title: "Error", message: localizedDescription, preferredStyle: .alert)
        let action = UIAlertAction(title: "OK", style: .default)
        alert.addAction(action)
        alert.show(completion: completion)
    }
}

The easiest way to handle UIAlertController in Swift

Shu — Mon, 12 Aug 2019 06:58:40 +0000

UIKit provides UIAlertController, but it is sometimes annoying to use. You have to get the top UIViewController. I will introduce an easier way to handle UIAlertController.

// AlertController.swift

UIKit 

class AlertController: UIAlertController {
    private lazy var alertWindow: UIWindow = {
        let window = UIWindow(frame: UIScreen.main.bounds)
        window.rootViewController = ClearViewController()
        window.backgroundColor = UIColor.clear
        window.windowLevel = UIWindow.Level.alert
        return window
    }()

    /// Shows a custom alert controller.
    func show(animated flag: Bool = true, completion: (() -> Void)? = nil) {
        guard let rootVC = alertWindow.rootViewController else { return }
        alertWindow.makeKeyAndVisible()
        rootVC.present(self, animated: flag, completion: completion)
    }
}

private class ClearViewController: UIViewController {
    override var preferredStatusBarStyle: UIStatusBarStyle {
        return UIApplication.shared.statusBarStyle
    }

    override var prefersStatusBarHidden: Bool {
        return UIApplication.shared.isStatusBarHidden
    }
}

You can use AlertController like following. This alert will allow you to show an alert view from anywhere easily. I mean, You don't have to call present(viewControllerToPresent: UIViewController>, animated: Bool, completion: (() -> Void)?) from UIViewController anymore.

func displayAlert() {
    let alert = AlertController(title: "Error", message: "Something happened", preferredStyle: .alert)
    let action = UIAlertAction(title: "OK", style: .default)
    alert.addAction(action)
    alert.show()
}

You might want to extend Error like below. You can show an error alert like error.displayAlert(). It's easy, isn't it?

extension Error {
    func displayAlert(completion: (() -> Void)? = nil) {
        let alert = AlertController(title: "Error", message: localizedDescription, preferredStyle: .alert)
        let action = UIAlertAction(title: "OK", style: .default)
        alert.addAction(action)
        alert.show(completion: completion)
    }
}

Firebase is AMAZING

Shu — Fri, 13 Jul 2018 12:42:30 +0000

I'm using Firebase these days, and I found it very easy to make native apps without coding server side. Firebase gives functions of authentication, analytics, push notifications, database, file storage, etc to developers. Besides, interestingly, the structure of Firestore/Realtime Database is not supposed to be ordinary, it's quite characteristic. Database schema should represent view itself, so normalization is not always good in Firebase. That's so oriented to native app developer.

I made a sample app using Firebase(Firestore, Cloud Messaging, Authentication) like following movie. When a user pushes Add Button , a new document will be saved in Firestore, and then this update triggers sending push notifications to this user.

Source code is in this repository.

https://github.com/ngo275/FirebaseSample

https://github.com/ngo275/FirebaseSampleFunctions