Swift之for循环

forEach

let numbers=[Int](0...7)
numbers.forEach{
   
    (num) in
    if(num==3){
   
    return
    }
    print(num)
}

for in
for in可以说比forEach好用太多

let numberList = [1,2,3,4,5]
 var result = ""
for num in numberList {
   
     result += "\(num) "
}

enumerated
普通的for循环无法拿到索引，通过关键字enumerated()可以拿到索引

let numbers=[Int](0...7)
for (index,num) in numbers.enumerated(){
   
    print("the index is :\(index)")
    print(num)
}

迭代器遍历

let numbers=[Int](0...7)
var numInerator = numbers.makeIterator()
while let num = numInerator.next() {
   

    print(num)
}

indices
讲到遍历就离不开索引，startIndex 返回第一个元素的位置，对于数组来说，永远都是0，endIndex 返回最优一个元素索引+1的位置等同于count，如果数组为空，startIndex 等于endeIndex
enumerated获取了索引和值
那么如果我们想只遍历索引呢，可以使用indices获取数组的索引区间

let numbers = [Int](2...7)
for i in numbers.indices{
   
    print(numbers[i])
}

Range

let numbers = [Int](2...7)
for i in 0...(numbers.count-1)
    print(numbers[i])
}

弃用
首先说一下，Swift 3.0 版本将会去掉沿用已经的 C 风格循环语法，以后此语法不会再swift中出现

for var i = 0; i < numberList.count; i++ {
   



         }