Iterating over multiple arrays with ForEach SwiftUI

Question

The ForEach struct in swiftUI is really useful for iterating over an array to create views, but I'm wondering if there is a way to iterate over multiple arrays at the same time. I know that if you use zip when you are using a for in loop you can achieve this like:

for (height, label) in zip(heights, labels) {
print("\(height) : \(label)")}

However, i'm wondering if it's possible to do this with a ForEach. I have tried, but I can't seem to get it right. The only way i've found to iterate over two arrays is to use an index to subscript each array, but that doesn't seem swifty enough.

What i've tried so far is:


let heights:[CGFloat] = [20, 40, 100, 5, 70, 80, 30]
let labels = ["mon", "tue", "wed", "thu", "fri", "sat", "sun", ]

ForEach(zip(heights, labels), id: \.self) { (height, label) in
                    Text("\(height)")
                    Text(label)
                }

But no joy, and the swiftUI errors are as cryptic as ever..... Any pointers gratefully received.

Edit: One way of getting it working that I have found is to do a nested ForEach, like:

ForEach(self.heights, id: \.self) { height in
                    Group {
                        Text("\(height)")
                        ForEach(self.labels, id: \.self) { label in

                            Text(label)
                        }
                    }
                }

But again, it doesn't seem very swifty.

It's completely off the mark. It's saying: Generic parameter 'Background' could not be inferred. I know that it has nothing to do with the actual problem, the compiler errors are just whack atm with swiftUI. — テッド
– テッド, Commented Feb 3, 2020 at 16:32

Martijn Pieters · Accepted Answer · 2022-08-23 07:10:44Z

31

Here is possible approach (tested & worked with Xcode 11.3.1)

ForEach(Array(zip(heights, labels)), id: \.0) { item in
    VStack {
        Text("\(item.0)")
        Text(item.1)
    }
}

edited Aug 23, 2022 at 7:10

Martijn Pieters

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answered Feb 3, 2020 at 16:46

Asperi

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5 Comments

テッド Over a year ago

Top man! using the id: \.0 was the trick then. Can you explain why this works and not \.self?

Asperi Over a year ago

id here is expected as keypath to Hashable property, but \.self in this case is tuple, while \.0 is CGFloat. The \.1 also can be used. In any case you have to provide something Hashable.

テッド Over a year ago

Makes sense! Thanks for taking the time to answer my question.

Shawkath Srijon Over a year ago

This is really good. But what if I have 3 arrays? How to solve in this case when zip works with only two sequences?

TheLivingForce Over a year ago

@ShawkathSrijon a bit late, but you can either do zip(a, zip(b, c)) or some github project like gist.github.com/tailec/bf37d064df79e5121def6fafbf1148b1 If you don't like the manual solution of multiple nested zips, you can always unbox them with a map. This will eliminate nested tuples: zip(a, zip(b, c)).map { ($0, $1.0, $1.1) }

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