Swift array to array of tuples

Question

I have the following two arrays:

let xaxis = ["monday", "tuesday", "wednesday", "thursday", "friday"]
let yaxis = [1, 2, 3, 4, 5]

I would like to merge them into an array that looks like this:

[ ("monday", 1), ("tuesday", 2), ("wednesday", 3), ("thursday", 4), ("friday", 5)]

This is not a dictionary that you are showing , its an array of tuples — 3stud1ant3
– 3stud1ant3, Commented Aug 28, 2017 at 3:02

Rob · Accepted Answer · 2023-03-29 22:10:46Z

24

Use zip and map:

let xaxis = ["monday", "tuesday", "wednesday", "thursday", "friday"]
let yaxis = [1, 2, 3, 4, 5]

let tuples = Array(zip(xaxis, yaxis))  // or `zip(xaxis, yaxis).map { ($0, $1) }`

I know you asked about a tuple, but you can also consider a custom object, e.g.:

struct Day {
    let name: String
    let value: Int
}

let names = ["monday", "tuesday", "wednesday", "thursday", "friday"]
let values = [1, 2, 3, 4, 5]

let days = zip(names, values).map(Day.init)

edited Mar 29, 2023 at 22:10

answered Aug 28, 2017 at 3:17

Rob

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5 Comments

3stud1ant3 Over a year ago

These methods are faster as compared to simple for loops or not, please give your suggestion

Rob Over a year ago

The above is my suggestion. Avoid premature optimization. Always use the most concise, most expressive syntax, and don't worry about optimization unless it can possibly have material impact. The performance difference is indistinguishable with 5 items. And it's practically nonexistent when doing release builds. All of that having been said, I wonder why you're using tuples at all. Or why are you using an array of string literals as opposed to Calendar.current.weekdaySymbols. There are many things I'd worry about before spending a second thinking about replacing zip/map with for loops.

Martheli Over a year ago

I used those two arrays as an example but the real app won't have months or any calendar data in the array. I just wanted an example of how to convert two arrays, one of type string and one of type int, into an array of tuples.

user652038 Over a year ago

.map { ($0, $1) } doesn't transform, so Array(zip(xaxis, yaxis)) is better, de-conflating the transform+Array.init that map normally entails.

Rob Over a year ago

Agreed. Array(zip(…)) is probably better. Thanks.

nayem · Accepted Answer · 2017-08-28 03:31:32Z

3

Try this:

let arrayMerged = zip(xaxis, yaxis).map { ($0, $1) }

or this:

let arrayMerged = Array(zip(xaxis, yaxis))

edited Aug 28, 2017 at 3:31

answered Aug 28, 2017 at 3:15

nayem

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1 Comment

Sentry.co Over a year ago

The latter answer is 👌 I wounder which is faster?

3stud1ant3 · Accepted Answer · 2017-08-28 03:20:27Z

2

Try this:

let xaxis = ["monday", "tuesday", "wednesday", "thursday", "friday"]

let yaxis = [1, 2, 3, 4, 5]

var newArr = [(String, Int)]()

for i in 0..<xaxis.count {
        newArr.append((xaxis[i], yaxis[i]))
}
print(newArr)

edited Aug 28, 2017 at 3:20

answered Aug 28, 2017 at 3:05

3stud1ant3

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1 Comment

rmaddy Over a year ago

This makes no use of the yaxis array.

sCha · Accepted Answer · 2017-08-28 03:17:53Z

1

let tuples = xaxis.enumerated().map { (index, value) in (value, yaxis[index]) }

Assuming yaxis's count always matches to xaxis.

edited Aug 28, 2017 at 3:17

answered Aug 28, 2017 at 3:09

sCha

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2 Comments

rmaddy Over a year ago

This also assumes the values in the xaxis array are unique.

yarlg Over a year ago

the code looks short and clean but has time complexity, if used on a large array. answer from 3stud1ant3 is recommended if considered time complexity

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