Swift 每隔一个项目追加到数组

Question

我有一个 swift 数组 "Monthdata"，我想在我的月份数组中附加每个第二个值。

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

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

基本上我的 monthData 数组看起来像：

["Aug 12","Oct 12"]

Answer 1

尝试使用模运算符 ( % )

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)

输出：

[Aug 12, Oct 12]

Answer 2

也可以使用swift数组filter方法得到过滤后的数组，

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

Answer 3

有一个更紧凑的版本可以按元素的索引过滤数组。

如何查找数组中第 N 个元素的示例 (swift 2.0):

let array = ["0", "1", "2", "3", "4", "5", "6", "7", "8", "9"]
let n = 2
let filteredArray =  array.enumerate().flatMap { [=10=].index % n == 0 ? [=10=].element : nil }

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

Answer 4

Swift 3（基于@maxkonovalov 的回答）

let array = ["0", "1", "2", "3", "4", "5", "6", "7", "8", "9"]
let step = 2
let filtered = array.enumerated().flatMap { [=10=].offset % step == 0 ? [=10=].element : nil }

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

Answer 5

要解决这个问题，您可以使用 Strides class and a map method:

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)

Swift 每隔一个项目追加到数组

Swift Append every second item to Array

arrays

enumeration

append

ios

swift