Swift How to break an array of objects into an array of arrays?

Question

I have an array of purchase objects [Purchase] defined as:

struct Purchase {
    let count: Int
    let food: String
}

How can I get turn this array of purchases into an array of arrays of purchases with the same count (Int)?

For example:

let input: [Purchase(count: 2, food: "popcorn"), Purchase(count: 3, food: "popcorn"),  Purchase(count: 2, food: "soda"),
            Purchase(count: 2, food: "popcorn"), Purchase(count: 2, food: "soda")]

output: [[Purchase]] = [[Purchase(count: 2, food: "popcorn"), Purchase(count: 2, food: "soda"),
          Purchase(count: 2, food: "popcorn"), Purchase(count: 2, food: "soda")], [Purchase(count: 3, food: "soda")]

Do you look for specific transformation logic or you just want to make each element trunk into an array of one element? — Aleksandr Medvedev
– Aleksandr Medvedev, Commented May 23, 2022 at 2:13
You can simply do this: let output = Array(Dictionary(grouping: input){$0.count}.values) — koropok
– koropok, Commented May 23, 2022 at 2:38
Purchase(count: 3, food: "soda") is not contained in input. — user652038
– user652038, Commented May 23, 2022 at 3:57

user652038 · Accepted Answer · 2022-05-23 03:57:09Z

1

The answer is in the comments but it can look a little cleaner.

Dictionary(grouping: input, by: \.count).map(\.value)

answered May 23, 2022 at 3:57

user652038

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