On 16.04.2016 5:00, Jacob Bandes-Storch via swift-evolution wrote:
I believe the community is in agreement about the following:
• The "allValues" behavior should be provided by conformance to some
protocol, named ValueEnumerable or ValuesEnumerable or similar.
• The compiler should derive an allValues implementation for "simple"
enums (those without associated values).
Please let me add my 2 cents. (Unfortunately can't support discussion on
suggested level, sorry for some simplicity)
I believe first of all we need a easy to use method to iterate enum cases
_without_ the need of manually specify each of case value in code for this.
I believe this is a huge problem we have now with enums. Ar at least Swift
compiler should force us to specify each of case values in such array.
I mean that we can now implement this allValues by just introduce an array
constant in enum{} declaration "manually". _But_ we need to change this
array accordingly each time we add new or change order of 'cases' in our
enum. And right now this is the place where we most likely will have errors
with forgotten values/wrong order.
Should we add extra complexity to Swift to implement the solution? I'm not
sure.
Can't compiler "just" generate some kind of
static let allValues : [Self] = [firstCase, secondCase, ..]
for each enum(and only enum)? Should we introduce a dozen of
protocols,extensions etc to implement such a solution just for enums?
enum ZZZ {
case One, Two
// this can be auto-generated
static let allValues: [ZZZ] = [.One, .Two]
}
As for generic enums, the best I can implement right now, is calculated
property:
enum AAA<T,Z> {
case One, Two // somehow T,Z is used here, not important
// I believe this could be also auto-generated
static var allValues : [AAA<T,Z>] { return [.One, .Two] }
}
As for the order of elements in allValues, IMO this order should be exactly
as defined in enum. We can know the Raw value for specified enum case
value, when we have it. But we can't say the defined position/index of enum
case if we'll have allValues ordered by raw value.
enum ZZZ: Int {
case One = 3, Two = 1
// autogenerated:
//static let allValues: [ZZZ] = [.One, .Two]
}
print(ZZZ.allValues) => [One, Two]
print(ZZZ.allValues[0].rawValue) => 3
if allValues will return [Two, One], we can't find out how these cases was
declared in our enum. I.e. in first case we have a solution(sort by
rawValue), in second case - we have no solution.
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