How to sum NSNumber array in Swift?

Question

How to sum NSNumber array in Swift? I'm getting this error when I use .reduce. any other way to sum the NSNumber array?

Cannot invoke 'reduce' with an argument list of type '(Int, _)

var record = [Record]()
var incomeFilter: [Record] = []

let formatter = NumberFormatter()
formatter.numberStyle = .currencyAccounting
formatter.currencySymbol = "¥"
formatter.maximumFractionDigits = 2
formatter.minimumFractionDigits = 2

incomeFilter = record.filter { $0.recordtype!.contains("Income") && $0.createdAt! == recordItem.createdAt!}
let incomeSumArray = incomeFilter.map{formatter.number(from: $0.amount!) ?? 0.00}.reduce(0, +)
//Cannot invoke 'reduce' with an argument list of type '(Int, _)
print(incomeSumArray)

//result without .reduce
//[9.99, 6.58, 7777.77]

Once again, why don't you first sum up the Double values and then use the number formatter and I explained the error message in my answer yesterday — vadian
– vadian, Commented Nov 19, 2017 at 7:55
I think I can't sum the double first, because some string have separator "," , so if I sum the double first, the number which above 1,000 will get nil. The separator break the string to double conversion routine. @vadian — Lester
– Lester, Commented Nov 19, 2017 at 8:04

Sulthan · Accepted Answer · 2017-11-19 07:47:38Z

3

I think the problem is using ?? 0 with an optional of type NSNumber. You always need the same type when nil-coalescing. You have to convert NSNumber to a numeric value (double) first:

let incomeSum = incomeFilter
    .map {
        formatter.number(from: $0.amount!)?.doubleValue ?? 0
     }
    .reduce(0, +)

or

let incomeSum = incomeFilter
    .map {
        guard
           let amountString = $0.amount,
           let number = formatter.number(from: amountString)
        else {
           return 0
        }

        return number.doubleValue
     }
    .reduce(0, +)

answered Nov 19, 2017 at 7:47

Sulthan

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Comments

Ahmad F · Accepted Answer · 2017-11-19 07:53:30Z

0

You could map the incomeFilter to be an array of doubles (incomeFilter.map{formatter.number(from: $0.amount!) ?? 0.00}) before reducing it:

let incomeSumArray = incomeFilter.map {
        formatter.number(from: $0.amount!) ?? 0.00
    }.map {
        $0.doubleValue
    }.reduce(0, +)

answered Nov 19, 2017 at 7:53

Ahmad F

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