Themer

Themer is a lightweight theme manager for iOS which provides theming for the whole app and allows toggling the current theme, all at once. It was developed by striving for the highest flexibility and cleanness of theming code and to provide a universal solution suitable even for pre-iOS 13 devices.

Table of Contents

• Features & Benefits
• How
• Get started
• Installation
  • Swift Package as dependendcy in Xcode 11+
  • Manually
• License

Features & Benefits

• A flexible and extensible theming facility to the entire app
• A clean theming code
• A clear boundary between the look and the logic
• Compatibility with pre-iOS 13 devices

How

By integrating Themer into your app and configuring. Here're the steps:

1. Instantiate the theme manager singleton, an instance of the Themer class.
2. Configure it with your app themes.
3. For each themable visual element, add a theme-handling method(s) and register it with Themer.
4. Whenever needed, toggle the current theme using Themer's theme property.

Get started

1. First, declare a model for your theme settings, which will represent a collection of the available theme attributes in your app, like in the example below.

   import Themer
   ...
   struct MyThemeSettings: ThemeModelProtocol {
       let appBgColor: UIColor
       let textColor: UIColor
   }

2. Define your themes (theme settings instances).

   extension MyThemeSettings {
       static let lightTheme = MyThemeSettings(
           appBgColor: .white,
           textColor: .black
       )
       static let darkTheme = MyThemeSettings(
           appBgColor: .gray,
           textColor: .white
       )
   }

   Here, the extension serves for better code organizing.

3. Declare your app's theme enum, which is the key in configuring and using the theme manager.

   import Themer
   ...
   enum MyTheme: ThemeProtocol {
       case light
       case dark
       var settings: MyThemeSettings {
           switch self {
           case .light: return MyThemeSettings.lightTheme
           case .dark: return MyThemeSettings.darkTheme
           }
       }
   }

   Here, the enum's cases behave like “tags” to refer to the available themes. The computed property settings maps the enum's cases to their respective theme instances.

4. To integrate the theme manager, in your app define the theme manager's singleton, as shown below.

   import Themer
   ...
   extension Themer where Theme == MyTheme {
       private static var instance: Themer?
       static var shared: Themer {
           if instance == nil {
               instance = Themer(defaultTheme: .light)
           }
           return instance!
       }
   }

   Notice how the theme manager is configured with the enum MyTheme (via the Theme generic parameter constraining with the where clause) , defined in step 3.

5. Define theme-handling method(s) for each themable visual element, like below for a hypothetical ThemableViewController, like in the example below.

   extension ThemableViewController {
       /// Handles Themer's theme toggle notifications.
       ///
       /// - Parameter theme: The new theme.
       private func handleTheme(_ theme: MyTheme) {
           view.backgroundColor = theme.settings.appBgColor
           ...
       }
   }

   The handleTheme(_:) method is where you put all theme configuring code for ThemableViewController. The theme-handler methods can be named arbitrarily. Specific theme attributes can be reached by referring to the settings property, which provides access to them.

6. Now, by using Themer's method register(target:action:) register ThemableViewController's theme-handling method(s), like in the example below.

   import Themer
   ...
   class ThemableViewController: UIViewController {
       override func viewDidLoad() {
           super.viewDidLoad()
           // Subscribe to theme notifications.
           Themer.shared.register(target: self,
                                  action: ThemableViewController.handleTheme)
       }
   }

   Note: you should register theme-handling method(s) in the point where their targets (i.e., the visual elements) are ready for immediate theming, as the initial theme applying (with the default theme) is performed at that very moment!

7. Whenever you need to toggle the current theme, you just write, as shown below.

   import Themer
   ...
   Themer.shared.theme = .dark

Installation

Swift Package as dependency in Xcode 11+

1. Go to "File" -> "Swift Packages" -> "Add Package Dependency"
2. Paste Themer repository URL into the search field:

https://github.com/SerhiyButz/Themer.git

3. Click "Next"

4. Ensure that the "Rules" field is set to something like this: "Version: Up To Next Major: 1.1.0"

5. Click "Next" to finish

For more info, check out here.

Manually

Simply Copy and Paste Source/Themer files in your Xcode Project.

License

This project is licensed under the MIT license.