How to create hash values from objects using Hasher

Swift version: 5.4

Paul Hudson @twostraws May 28th 2019

Hash values are an invaluable way of identifying data uniquely, and any type that conforms to the Hashable protocol can be used to create all or part of a hash value by using the Hasher struct.

To use this, create an instance of Hasher, provide it with whatever objects you want to hash, then call finalize() to generate the final value as an integer. For example:

struct iPad: Hashable {
    var serialNumber: String
    var capacity: Int
}

let first = iPad(serialNumber: "12345", capacity: 128)
let second = iPad(serialNumber: "abcde", capacity: 512)

var hasher = Hasher()
hasher.combine(first)
hasher.combine(second)
let hash = hasher.finalize()