【Swift 60秒】18 - Enum raw values

0x00 Lesson

Sometimes you need to be able to assign values to enums so they have meaning. This lets you create them dynamically, and also use them in different ways.

For example, you might create a Planet enum that stores integer values for each of its cases:

enum Planet: Int {
	case mercury
	case venus
	case earth
	case mars
}

Swift will automatically assign each of those a number starting from 0, and you can use that number to create an instance of the appropriate enum case. For example, earth will be given the number 2, so you can write this:

let earth = Planet(rawValue: 2)

If you want, you can assign one or more cases a specific value, and Swift will generate the rest. It’s not very natural for us to think of Earth as the second planet, so you could write this:

enum Planet: Int {
	case mercury = 1
	case venus
	case earth
	case mars
}

Now Swift will assign 1 to mercury and count upwards from there, meaning that earth is now the third planet.

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0x01 Tips

Raw values let us give each of our enum cases a value so they are more than just names.

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