Call Array.reduce(_:_) from enumerated array

Question

Normal reduce call:

[1,2,3].reduce(0, { cur, val in
  return val
})

Attempt at calling reduce from an EnumeratedSequence<Array<Element>>:

    [1,2,3].enumerated().reduce(0, { cur, (index, element) in
      return element
    })
  // Error: consecutive statements on a line must be separated by ';'" (at initial reduce closure)

let result = [1,2,3].enumerated().reduce(0) { $0 + $1.element } — Leo Dabus
– Leo Dabus, Commented Apr 3, 2017 at 14:10
Related: Destructuring tuple of tuple in closure & Map or reduce with index in Swift — Hamish
– Hamish, Commented Apr 3, 2017 at 14:24

vacawama · Accepted Answer · 2017-04-03 14:03:22Z

6

You can access the element of the tuple with val.element and the index with val.offset:

let result = [1,2,3].enumerated().reduce(0, { cur, val in
    return val.element
})

Alternatively, you can use assignment to access the values in the tuple:

let result = [1,2,3].enumerated().reduce(0, { cur, val in
    let (index, element) = val
    return element
})

edited Apr 3, 2017 at 14:03

answered Apr 3, 2017 at 13:56

vacawama

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1 Comment

JeremyP Over a year ago

It's a slight restriction on Swift that you can't "expand" tuples in a closure's parameter list, which is the underlying problem with the code as per the question

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