SipHashable

public protocol SipHashable: Hashable

A variant of Hashable that makes it simpler to generate good hash values.

Instead of hashValue, you need to implement addHashes, adding data that should contribute to the hash to the supplied hasher. The hasher takes care of blending the supplied data together.

Example implementation:

struct Book: SipHashable {
    var title: String
    var pageCount: Int

    func appendHashes(to hasher: inout SipHasher) {
        hasher.append(title)
        hasher.append(pageCount)
    }

    static func ==(left: Book, right: Book) -> Bool {
        return left.title == right.title && left.pageCount == right.pageCount
    }
}