EducaSwift

RawValue

We can assign a value to each of the cases of an enum. The most commonly used types for this are Int and String.

Let's see an example where we have an enum of type Int. When we assign a value to the first case, the following cases will automatically get the next value in order, although we can assign any value to each case if we choose.

enum Planet: Int {
    case mercury = 1
    case venus
    case earth
    case mars
    case jupiter
    case saturn
    case uranus
    case neptune
}

print(Planet.mercury.rawValue) // 1
print(Planet.mars.rawValue) // 4

In the case of using an enum of type String, we can also assign values. If we don't assign any, the name of the case will be used as the value.

enum Planet: String {
    case mercury = "Mercury"
    case venus
    case earth = "Earth"
    case mars = "Mars"
    case jupiter
    case saturn = "Saturn"
    case uranus = "Uranus"
    case neptune = "Neptune"
}

print(Planet.mercury.rawValue) // Mercury
print(Planet.jupiter.rawValue) // jupiter

Not only can we retrieve the rawValue of an enum, but we can also create them using Strings or Ints.

This init returns an Optional value, since it is possible that the provided value might not match any of the cases.

let myPlanet = Planet(rawValue: "Mars")
print(myPlanet) // Optional(Planet.mars)

let myPlanetTwo = Planet(rawValue: "venus")
print(myPlanetTwo) // Optional(Planet.venus)

let myPlanetFail = Planet(rawValue: "mars")
print(myPlanetFail) // nil

Enums and Decodable

You can add an enum property to your Decodable object. If the value on the JSON matches the RawValue of the enum, it will be converted. To be able to do this, our enum should also adopt Decodable protocol.

import Foundation

enum Planet: String, Decodable {
    case mercury = "Mercury"
    case venus = "Venus"
    case earth = "Earth"
    case mars = "Mars"
    case jupiter = "Jupiter"
    case saturn = "Saturn"
    case uranus = "Uranus"
    case neptune = "Neptune"
}

struct Person: Decodable {
    let planet: Planet
}

let jsonString = """
    { "planet": "Earth" }
"""

if let data = jsonString.data(using: .utf8),
   let me = try? JSONDecoder().decode(Person.self, from: data) 
{
    print(me)
}

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