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})
2.index(符合条件的索引):返回int值 let arr = [1,0] //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") }