Add struct to array property using shorthand

Question

Add struct to array property using shorthand

I have an array of items

struct Item {
    var id: String
}

How can I add all ids to an array using the reduce function ?

What I am trying:

self.items.reduce([String](), { $0.0.append($0.1.id)})

But compilation shows an error:

The contextual closure type '(_, [Item]) → _' expects 2 arguments, but 1 was used in the closure body

+3

swift

Zigii wong 02 Aug 17 at 14:40

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3 answers

Try the following:

items.reduce([String](), { res, item in
    var arr = res
    arr.append(item.id)
    return arr
})

+1

paulvs 02 Aug 17 at 14:47

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You probably mean map

, notreduce

let ids = items.map{ $0.id }

+1

vadian 02 Aug 17 at 14:50

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Tobol · Accepted Answer · 2017-08-02T14:54:33+0000

If you want to do it with shorthand, here is a snippet for Swift 3 and 4:

struct Item {
    var id: String
}

var items = [Item(id: "text1"), Item(id: "text2")]
let reduceResult = items.reduce([String](), { $0 + [$1.id] } )
reduceResult // ["text1", "text2"]

There were 2 problems:

Shortening gives you 2 arguments, not one tuple with 2 values
You cannot edit the argument passed to you in the block, you must return a new object

But in this case, the best solution is to use a map:

let reduceResult = items.map { $0.id }

Add struct to array property using shorthand

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