This is nice, but it doesn’t solve the issue at hand because there is only one
enum value. I would like to have something like:
if value == .TWO { … }
I can’t use this == operator for this because I’d have to create:
if value == .TWO(str) { … }
But I don’t have a specific str, and I want the condition to be true no matter
what the value of str is.
Andy
> On Jan 17, 2017, at 10:53 PM, Rien <r...@balancingrock.nl> wrote:
>
> A guy named Matthias recently commented this on my blog:
>
> func == (left: Enum3, right: Enum3) -> Bool {
> switch (left, right) {
> case (.ONE, .ONE):
> return true
> case (.TWO(let str1), .TWO(let str2)):
> return str1 == str2
> default:
> return false
> }
> }
>
> http://swiftrien.blogspot.nl/2015/05/swift-enum-compare-design-pattern.html
>
> Regards,
> Rien
>
> Site: http://balancingrock.nl
> Blog: http://swiftrien.blogspot.com
> Github: http://github.com/Swiftrien
> Project: http://swiftfire.nl
>
>
>
>
>> On 18 Jan 2017, at 01:15, Andy Chou via swift-evolution
>> <swift-evolution@swift.org> wrote:
>>
>> Enums with associated values can be very useful in Swift, but once you add
>> associated values you lose some properties, especially equality:
>>
>> ```
>> enum AuthenticationResponse {
>> case success
>> case alert(Alert)
>> case reauthenticate
>> }
>> ```
>>
>> Testing for a specific case requires a switch statement or the if pattern
>> match syntax:
>>
>> if case .success = response { … }
>>
>> But while this works well for control flow, it doesn’t work well for cases
>> where we want a Bool, such as assert(). There are also common situations
>> with lists and libraries like RxSwift where a filtering function uses a Bool
>> valued closure. In these situations the best we can do is write functions
>> like:
>>
>> ```
>> enum AuthenticationResponse {
>> case success
>> case alert(Alert)
>> case reauthenticate
>>
>> var isSuccess: Bool {
>> if case .success = self {
>> return true
>> } else {
>> return false
>> }
>> }
>>
>> var isReauthenticate: Bool {
>> if case .reauthenticate = self {
>> return true
>> } else {
>> return false
>> }
>> }
>>
>> var isAlert: Bool {
>> if case .alert(_) = self {
>> return true
>> } else {
>> return false
>> }
>> }
>> }
>> ```
>> Any suggestions better than writing out each of these functions explicitly?
>>
>> The conditional conformances proposal coming in Swift 4 solves some of this
>> issue, but not completely. If Alert isn’t Equatable, it is still useful to
>> test whether the result is .success. For example:
>>
>> assert(response == .success)
>>
>> This is perfectly intelligible and I would argue that equality should be
>> defined for enums with associated values omitted:
>>
>> assert(response == .alert)
>>
>> Here we are ignoring the associated values, and merely checking if the enum
>> case is the same.
>>
>> Andy
>>
>> _______________________________________________
>> swift-evolution mailing list
>> swift-evolution@swift.org
>> https://lists.swift.org/mailman/listinfo/swift-evolution
>
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