Swift中 String、Array、Set、Dictionary的遍历方法

方法1：
var str  = "china"
for item in str.characters{
print(item)
}

方法2：
var str  = "china"
for item in str.characters.indices{
print(str[item])
}

方法3：
var str  = "china"
var i = 0
while i < str.characters.count {
var index = str.index(str.startIndex, offsetBy: i)
print(str[index])
i += 1

}

方法1：
var arr = [23,1,45,21,66,78]
for item in arr{
print(item)
}

方法2：
var arr = [23,1,45,21,66,78]
for(index,value) in arr.enumerated(){
print(index,value)
}

方法3
var arr = [23,1,45,21,66,78]
var j = 0
while j < arr.count {
print(arr[j])
j += 1
}

var set:Set<String> = []
set = ["China","BeiJing","GuangZhou"]

for item in set{
print(item)
}

方法1：
var dic = [1001:"C",1002:"OC",1003:"IOS",1004:"Java"]
dic[1005] = "C++" // 增加值
dic[1001] = "C#" // 改变1001的值

for item in dic{
print(item)
}

方法2：
var dic = [1001:"C",1002:"OC",1003:"IOS",1004:"Java"]
for item in dic.keys{
print(item,dic[item]!)
}

方法3：
var dic = [1001:"C",1002:"OC",1003:"IOS",1004:"Java"]
for item in dic.values
{
print(item)
}