Swift Adds every second element to an array.

Question

I have a quick "Monthdata" array that I want to add every second value to the months array.

var monthData = []
let months = ["Jul 12","Aug 12","Sep 12","Oct 12"]

for month in months {
 self.monthData.append(month)
}

So basically I create an array of monthData:

["Aug 12","Oct 12"]

Answer 1

Try using modulo operator (%)

var monthData = Array<String>()
let months = ["Jul 12","Aug 12","Sep 12","Oct 12"]

var i : Int = 1

for month in months{
    if(i%2 == 0){
        monthData.append(month)
    }
    i = i + 1
}

println(monthData)

Output:

[August 12, October 12]

Answer 2

You can also use the swift array method filterto get a filtered array,

monthData = months.filter{ (dataValue) in (find(months, dataValue)! % 2 != 0) }

Answer 3

Swift 3 ( @maxkonovalov)

let array = ["0", "1", "2", "3", "4", "5", "6", "7", "8", "9"]
let step = 2
let filtered = array.enumerated().flatMap { $0.offset % step == 0 ? $0.element : nil }

// filtered: ["0", "2", "4", "6", "8"]

Answer 4

.

, N- (swift 2.0):

let array = ["0", "1", "2", "3", "4", "5", "6", "7", "8", "9"]
let n = 2
let filteredArray =  array.enumerate().flatMap { $0.index % n == 0 ? $0.element : nil }

// filteredArray = ["0", "2", "4", "6", "8"]

Answer 5

, Strides map:

let months = ["Jul 12","Aug 12","Sep 12","Oct 12"]
let monthData = stride(from: 1, to: months.count, by: 2).map { (value:Int) -> String in
    return months[value]
}
print(monthData)