How to convert array of enum to array of int's

Question

I am using Core Data and one of my predicates retrieves data based on the following enum:

enum Period : Int {
   Daily
   Weekly
   Monthly
}

My predicates is like this:

public static func byTypePredicate(periods: [Int]) -> NSPredicate {
    return NSPredicate(format: "period IN %@", periods)
}

My problem is I don't want to use Int's when calling this predicate, I want to pass the Period enum, but inside the predicate is have to convert it to Int to make it work.

Is there a quick way to convert it ?

Side note: As of Swift 3, the convention is to start enumeration cases with a lowercase letter: daily, weekly, monthly. — Martin R
– Martin R, Commented Sep 27, 2016 at 18:23

Martin R · Accepted Answer · 2016-09-27 18:09:30Z

5

You can use the map() method (of the Sequence protocol) to map each enumeration to its integer raw value:

func byTypePredicate(periods: [Period]) -> NSPredicate {
    let intPeriods = periods.map { $0.rawValue } // [Int]
    return NSPredicate(format: "period IN %@", intPeriods)
}

edited Sep 27, 2016 at 18:09

answered Sep 27, 2016 at 18:04

Martin R

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1 Comment

Adrian Over a year ago

That's so elegant. I like it.

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