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.
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
}