Matching optional enums against non-optionals

Paul Hudson      @twostraws

Swift has always been smart enough to handle switch/case pattern matching between optionals and non-optionals for strings and integers, but before Swift 5.1 that wasn’t extended to enums.

Well, in Swift 5.1 we can now use switch/case pattern matching to match optional enums with non-optionals, like this:

enum BuildStatus {
    case starting
    case inProgress
    case complete
}

let status: BuildStatus? = .inProgress

switch status {
case .inProgress:
    print("Build is starting…")
case .complete:
    print("Build is complete!")
default:
    print("Some other build status")
}

Swift is able to compare the optional enum directly with the non-optional cases, so that code will print “Build is starting…”

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Other changes in Swift 5.1…

• Improvements to synthesized memberwise initializers
• Implicit returns from single-expression functions
• Universal Self
• Opaque return types
• Static and class subscripts
• Warnings for ambiguous none cases
• Ordered collection diffing
• Creating uninitialized arrays

Download all Swift 5.1 changes as a playground Link to Swift 5.1 changes

Browse changes in all Swift versions