CODEWITHSUNDEEP
arraysswiftfor-looptuples
kuemme01
kuemme01

Reputation: 472

How to get a tuple from two lists of elements

I have two lists of UIViews, some of that UIViews have an accessibilityIdentifier most of them are nil. I'm searching for a way to generate a tuple(or something) with the two UIViews from the lists that have the same accessibilityIdentifier.

The lists are not sorted or something.

Is there a way to not iterate multiple times through the second list to find every pair?

for view in firstViewList {
   if view.accessibilityIdentifier != nil {
       for secondView in secondViewList {
           if secondView.accessibilityIdentifier != nil && secondView.accessibilityIdentifier == view.accessibilityIdentifier {
               viewPairs.append((firstView: view, secondView: secondView))
           }
       }
   }
}

I think this is not very efficient.

Upvotes: 0

Views: 112

Answers (3)

Joakim Danielson
Joakim Danielson

Reputation: 51973

This solution creates an array of tuples with views from the first and second list respectively

var viewArray: [(UIView, UIView)]
firstViewList.forEach( { view in
    if let identifier = view.accessibilityIdentifier {
       let arr = secondViewList.filter( {$0.accessibilityIdentifier == identifier} )
        arr.forEach( { viewArray.append((view, $0))})
    }
})

Upvotes: 0

Alexander
Alexander

Reputation: 63271

Make a dict that indexes both view lists by their ID, filter out the ones where the ID is nil, and then use the keys common to both dicts to create a new dict that indexes pairs of same-id views.

Here's a rough example (which I haven't compiled myself).

func makeDictByAccessibilityID(_ views: [UIView]) -> [AccessibilityID: UIView] {
    return Dictionary(uniqueKeysWithValues:
        firstViewList
            .lazy
            .map { (id: $0.accessibilityIdentifier, view: $0) }
            .filter { $0.id != nil }
    )
}

viewsByAccessibilityID1 = makeDictByAccessibilityID(firstViewList)
viewsByAccessibilityID2 = makeDictByAccessibilityID(secondViewList)
commonIDs = Set(viewsByAccessibilityID1.keys).intersecting(
                Set(viewsByAccessibilityID2.keys)
            )

let viewPairsByAccessibilityID = Dictionary(uniqueKeysWithValues:
    commonIDs.lazy.map { id in
        // Justified force unwrap, because we specifically defined the keys as being available in both dicts.
        (key: id, viewPair: (viewsByAccessibilityID1[id]!, viewsByAccessibilityID2[id]!))
    }
}

This runs in O(n) time, which is the best you can get for this problem.

Upvotes: 1

Ali Adam
Ali Adam

Reputation: 331

I think you should first filtered your two arrays from the nil value then you can do like this 

let tempfirstViewList = firstViewList.filter { (view) -> Bool in
view.accessibilityIdentifier != nil
}
var tempsecondViewList = secondViewList.filter { (view) -> Bool in
view.accessibilityIdentifier != nil
}
tempfirstViewList.forEach { (view) in
let filterdSecondViewList = tempsecondViewList.filter { (secondView) -> Bool in
     secondView.accessibilityIdentifier == view.accessibilityIdentifier
}
if let sView = filterdSecondViewList.first {
    viewPairs.append((firstView: view, secondView: sView))
//after add it to your tuple remove it from the temp array to not loop throw it again
    if let index = tempsecondViewList.firstIndex(of: sView) {
        tempsecondViewList.remove(at: index)
    }
}
}

Upvotes: 0

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