Looping through a multidimensional array in swift

Question

So I am trying to iterate over an NSArray. My NSArray is an array of an array of strings. Here is a copy-paste of the first 1.5 elements

(
    (
    "Tater Tot Nachos",
    "Fried Feta",
    "The Ultimate Feta Bread",
    "Cheese Bread",
    "Aubrees Bread",
    "The Wings!",
    "Coconut Grove Chicken Sicks",
    "Far East Wings",
    "Bacon Brussels Sprouts"
),
    (
    "Shaved Brussels Sprout Salad",
    "Greek Salad",
    "Coronado Cobb Salad",
    "Harvest Salad",

This is the function that's giving me the headache

 func createMenu() {
    if let list = cellDescripters {
        for(index, item) in list.enumerated() {
            for food in item {
                //DO SOMETHING WITH "FOOD"
            }

        }
    }
}

' cellDescripters ' Is a global variable and it is the array I was outlining at the top, basically an array of arrays of strings.

When I print the type of ' item ' I see it's of type __NSArrayM which is an NSMutableArray from my understanding. Looking at documentation NSMutableArrays are iterable.

However when I go to compile this code I get the error:

Type 'Any' does not conform to protocol 'Sequence'

Any help would be greatly appreciated.

Well I am reading data from a plist file into that array. Why NSArray? I'm not entirely sure, I was following a tutorial. How else could I read in data from a plist file? — Nate Schreiner
– Nate Schreiner, Commented Feb 7, 2018 at 4:32
change cellDescripters type to [[String]] instead of NSMutableArray. — adarshaU
– adarshaU, Commented Feb 7, 2018 at 4:56

Jaydeep Vyas · Accepted Answer · 2018-02-07 04:59:42Z

8

I think following example give you help for example i have array of string array like you =

[["beverages", "food", "suppliers"],["other stuff", "medicine"]];

  var arrayExample = [["beverages", "food", "suppliers"],["other stuff", "medicine"]];
//Iterate array through for loop 
       for(index, item) in arrayExample.enumerated() 
         {
            for food in item 
             {
                print("index : \(index) item: \(food)")
            }
       }

OUTPUT

index : 0 item: beverages
index : 0 item: food
index : 0 item: suppliers
index : 1 item: other stuff
index : 1 item: medicine

answered Feb 7, 2018 at 4:59

Jaydeep Vyas

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1 Comment

Jaydeep Vyas Over a year ago

sorry i cant understand, you mean to say you have to prepare dictionary like ["0":[beverages","xyx","abc"], "1":[other stuff","medecine"]] right

Endanke · Accepted Answer · 2020-05-26 08:58:50Z

Here's a more generic solution for iterating 2D arrays in Swift. Tested in Swift 4 on iOS 13. Works only on Swift arrays, see the following link for converting your NSArray to Arrays: https://stackoverflow.com/a/40646875/1960938

// 2D array extension explanation: https://stackoverflow.com/a/44201792/1960938
fileprivate extension Array where Element : Collection, Element.Index == Int {

    typealias InnerCollection = Element
    typealias InnerElement = InnerCollection.Iterator.Element

    func matrixIterator() -> AnyIterator<InnerElement> {
        var outerIndex = self.startIndex
        var innerIndex: Int?

        return AnyIterator({
            guard !self.isEmpty else { return nil }

            var innerArray = self[outerIndex]
            if !innerArray.isEmpty && innerIndex == nil {
                innerIndex = innerArray.startIndex
            }

            // This loop makes sure to skip empty internal arrays
            while innerArray.isEmpty || (innerIndex != nil && innerIndex! == innerArray.endIndex) {
                outerIndex = self.index(after: outerIndex)
                if outerIndex == self.endIndex { return nil }
                innerArray = self[outerIndex]
                innerIndex = innerArray.startIndex
            }

            let result = self[outerIndex][innerIndex!]
            innerIndex = innerArray.index(after: innerIndex!)

            return result
        })
    }

}

An example usage:

let sampleMatrix = [
    ["a", "b", "c"],
    ["d", "e"],
    [],
    ["f"],
    []
]

// Should print: a, b, c, d, e, f      
for element in sampleMatrix.matrixIterator() {
    print(element)
}

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