ExpressibleByArrayLiteral in Swift

Photo by Pawel Czerwinski on Unsplash

When working with structs, you may encounter ExpressibleByArrayLiteral in a number of situations. It may seem obscure at first glance, but it’s helpful to know how it actually works and what it provides.

ExpressibleByArrayLiteral, as its very name signifies, is a protocol that allows the type it conforms to be initialized using an array literal. Additionally, it can increase readability. For clarity, you will examine this as a simple example.

Say, you’ve a Stack which its type is struct.

struct Stack<Element: Equatable>: Equatable {
  /// Holds the stack data.
  private var storage: [Element] = []
  
  init() { }
}

When you initialize the Stack, you have to initialize like this:

let stack = Stack(["expressible", "by", "array", "literal"]

However, if you add ExpressibleByArrayLiteral extension to the Stack:

extension Stack: ExpressibleByArrayLiteral {
  init(arrayLiteral elements: Element…) {
    storage = elements
  }
}

You could initialize the Stack like this:

let stack: Stack = ["expressible", "by", "array", "literal"]

The implementation is that simple! You can now try it out on your own project(s). You can access the GitHub repository where I used this here.

Thanks for reading!