CODEX

Swift: Key Path Basics

Learn what KeyPaths are and how you can use them.

Photo by Joshua Reddekopp on Unsplash

Keypaths in Swift

Keypaths offer a dynamic and type-safe way of referencing properties of a type.

KeyPath<ObjectType, PropertyType>

A key path is a reference to a property, not to the value of the property.

In practice, key paths allow you to refer to the same property in multiple places using the same key path variable. If you want to change the property you need to change it only in one place.

Retrieving and Modifying Properties with Key Paths

You can use key paths to retrieve and modify the values of properties.

As an example, let’s say you have a structure Fruit:

struct Fruit {
    var name: String
    var color: String
}

You can obtain a reference to the name property of the Fruit structure by defining a key path:

let keyPath = \Fruit.name

But what can you do with it?

You can use this keyPath reference as a subscript to a Fruit instance to retrieve its name:

var banana = Fruit(name: "Banana", color: "Yellow")