[swift-users] Reducing Array<OptionSet> to OptionSet

[Erica Sadun]

Maybe something like this? Or you could just bitwise || individual sets. Or you could use a dictionary to lookup [string: rawValue]. etc.

public struct MyOptionSet: OptionSet {
    public static let one = MyOptionSet(rawValue: 1 << 0)
    public static let two = MyOptionSet(rawValue: 1 << 1)
    public static let three = MyOptionSet(rawValue: 1 << 2)
    
    public var rawValue: Int { return _rawValue }
    public init(rawValue: Int) { self._rawValue = rawValue }
    private let _rawValue: Int
    
    private enum StringEnum: String { case one, two, three }
    public init(strings: [String]) {
        var set = MyOptionSet()
        strings.flatMap({ StringEnum(rawValue: $0) })
            .flatMap({ MyOptionSet(rawValue: 1 << $0.hashValue) })
            .forEach { set.insert($0) }
        _rawValue = set.rawValue
    }
}

let stringArray: [String] = ["one", "three"]
let stringOptions = MyOptionSet(strings: stringArray)
stringOptions.rawValue

> On Nov 3, 2016, at 7:09 PM, Jon Shier via swift-users <swift-users at swift.org> wrote:
> 
> Swifters:
> 	I’m dealing with a JSON API where sets of options are returned as arrays of strings. Representing these as OptionSets seems ideal. I can decode the arrays of strings into an array of individual OptionSet values, but I’ve run into a dead end when trying generically reduce the array of OptionSets to a single OptionSet value. I’ve tried variety of ways of definition a Collection extension, even tried defining a global function, but I can’t seem to use the OptionSet sequence initializer or reduce itself (cannot invoke insert with argument of type (OptionSet) (or T)). Any guidance here? 
> 	Here’s what I’ve tried:
> 
> extension Collection where Iterator.Element == OptionSet {
> 
>    func reduced() -> Iterator.Element {
>        return reduce(Iterator.Element()) {
>            var newResult = $0
>            newResult.insert($1)
>            return newResult
>        }
>    }
> 
> }
> 
> extension Collection where Iterator.Element == OptionSet {
> 
>    func reduced<T: OptionSet>() -> T {
>        return reduce(T()) {
>            var newResult = $0
>            newResult.insert($1)
>            return newResult
>        }
>    }
> 
> }
> 
> 
> extension Collection where Iterator.Element == OptionSet {
>    func reduced() -> Iterator.Element {
>        return Iterator.Element(self)
>    }
> }
> 
> func reduced<T: OptionSet>(_ options: [T]) -> T {
>    return options.reduce(T()) {
>        var newResult = $0
>        newResult.insert($1)
> 
>        return newResult
>    }
> }
> 
> Jon Shier
> _______________________________________________
> swift-users mailing list
> swift-users at swift.org
> https://lists.swift.org/mailman/listinfo/swift-users

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