Custom Initializers

Imagine you'd want to initialize an enum with custom data. In our example we have a Device enum that represents Apple devices and we'd like to also initialize them with non-standard names. Here's the enum:

enum Device {

   case appleWatch

}

Now if a user accidentally enters iWatch as their device, we still want to map this to the correct AppleWatch case. To do that, we will implement a custom initializer that sets self to the correct type:

enum Device { 

     case appleWatch 

     init?(term: String) {

       if term == \"iWatch\" {

           self = .appleWatch

       } else {

           return nil

       }

     }

}

In the above example, we used a failable initializer. However, normal initializers work just as well:

enum NumberCategory {

    case small

    case medium

    case big

    case huge



    init(number n: Int) {

         if n < 10000 { self = .small }

         else if n < 1000000 { self = .medium }

         else if n < 100000000 { self = .big }

         else { self = .huge }

    }

}