How to make a Swift enum with associated values equatable

Question

I have an enum of associated values which I would like to make equatable for testing purposes, but do not know how this pattern would work with an enum case with more than one argument.

For example, summarised below I know the syntax for making heading equatable. How would this work for options, which contains multiple values of different types?

enum ViewModel {     case heading(String)     case options(id: String, title: String, enabled: Bool) }  func ==(lhs: ViewModel, rhs: ViewModel) -> Bool {     switch (lhs, rhs) {     case (let .heading(lhsString), let .heading(rhsString)):         return lhsString == rhsString     case options...     default:         return false     } } 

I know Swift 4.1 can synthesize conformance for Equatable for us, but at present I am not able to update to this version.

Answer 1

SE-0185 Synthesizing Equatable and Hashable conformance has been implemented in Swift 4.1, so that it suffices do declare conformance to the protocol (if all members are Equatable):

enum ViewModel: Equatable {     case heading(String)     case options(id: String, title: String, enabled: Bool) } 

For earlier Swift versions, a convenient way is to use that tuples can be compared with ==.

You many also want to enclose the compatibility code in a Swift version check, so that the automatic synthesis is used once the project is updated to Swift 4.1:

enum ViewModel: Equatable {     case heading(String)     case options(id: String, title: String, enabled: Bool)          #if swift(>=4.1)     #else     static func ==(lhs: ViewModel, rhs: ViewModel) -> Bool {         switch (lhs, rhs) {         case (let .heading(lhsString), let .heading(rhsString)):             return lhsString == rhsString         case (let .options(lhsId, lhsTitle, lhsEnabled), let .options(rhsId, rhsTitle, rhsEnabled)):             return (lhsId, lhsTitle, lhsEnabled) == (rhsId, rhsTitle, rhsEnabled)         default:             return false         }     }     #endif }