swift 数组 的一些快速方法

?

1 2 3 4 5 6 7 8 9 10 11 12

1. filter (过滤器)：返回符合条件的一个数组                 let arr = [1,5,6,7,10,0]                //写法1                 let arr1 = arr.filter { (item) -> Bool in                     return item % 2 == 0                 }                                   //写法2                 let resultArray = arr.filter { return $0%2 == 0 }                        //写法3                 let arr2 = arr.filter({return $0%2 == 0})

　　

?

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18

2.index(符合条件的索引)：返回int值                 let arr = [1,5,6,7,10,0]                 //写法1：swift 4.0                 let index = arr.index(where: {$0 == 1})                                   //swift4.2  firstIndex:从前往后遍历，                 let index2 = arr.firstIndex(where:{$0 == 1})                 let index3 = arr.firstIndex { (item) -> Bool in                     return item == 1                 }                                   //lastIndex:c从后往前遍历                 let index4 = arr.lastIndex(where:{$0 == 1})                                   let index5 = arr.lastIndex(of: 5)                 if index5 != nil{                     print("打印一下")                 }

　　

?

1 2 3 4 5 6 7 8 9 10 11

3. contains(包含)：返回bool值                 let arr = [1,5,6,7,10,0]                 //写法1                 let isContains = arr.contains(where: {$0 == 3})                 //写法2                 let isContains1 = arr.contains { (item) -> Bool in                     return item == 100                 }                 //写法3 直接调用函数                  arr.contains(10)                 print(arr.contains(3))

　　

?

1 2 3 4 5 6 7 8

4. foreach: 和for in快速遍历 类似， 但是return 条件时，返回不一样           if self.view.subviews.count > 0{             self.view.subviews.forEach({$0.removeFromSuperview()})         }   注意点： 在使用return关键字的时候，很明显，for in中是当符合当前执行语句时，程序直接终止到此并返回, 比如上面的元素 "4"、"5"、"Hello World" 没有被执行；而forEach中是当符合当前执行语句时，程序跳过本次判断继续执行， 比如上面的元素"4"、"5"、"Hello World"被执行。foreach: 和for in 具体区别：https://www.jianshu.com/p/0f75c23773b5

　　

 

 

数组的  compactMap 添加每个元素

 let numberArr :[Substring]= “123,5215614,”.split(separator: ",")
 
 let arrayStrings: [String] = numberArr.compactMap { "\($0)" }