for－in的使用

对Range使用for－in

for number in 1..<10{
    number
}

对string.characters使用for-in

for c in "hello".characters{
    c
}

对Array使用for-in

var vowels = ["a","s","d","f"]
for vowel in vowels{
    vowel
}

for (i,vowel) in vowels.enumerate(){
    i
    vowel
}

对Dictionary使用for-in

var dict = [1:"A",2:"B",3:"C"]
for key in dict.keys{
    key
}
for value in dict.values{
    value
}
for (key,value) in dict{
    key
    value
}

对set使用for-in

var set = Set(vowels)
for vowel in set {
    vowel
}

//奇奇怪怪的类型
"hello".characters
vowels.enumerate()
dict.keys

//可迭代