在Swift中的数组中插入新元素

代码：

让oldNums:[Int]=[1,2,3,4,5,6,7,8,9,10]
var newArray=oldNums[1..
oldNums[1..
oldNums[1。。
let oldNums: [Int] = [1, 2, 3, 4, 5 ,6 , 7, 8, 9, 10]
var newArray = oldNums[1..<4]
newArray.insert(99, atIndex: 0) // <-- crash here
newArray.insert(99, atIndex: 1) // <-- work very well

let oldNums: [Int] = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
var newArray = oldNums[1..<4]
print(newArray.indices)
// 1..<4

newArray.insert(99, atIndex: 0)

newArray.insert(99, atIndex: newArray.startIndex)

let oldNums: [Int] = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
var newArray = Array(oldNums[1..<4])
print(newArray.indices)
// 0..<3

newArray.insert(99, atIndex:0)
print(newArray)
// [99, 2, 3, 4]