一、 之前学习swift时,使用characters进行遍历
let str = "Hello world!"
for s in str.characters {
print(s)
}
在swift3之后该方法被放弃，直接对String类型进行遍历
let str = "Hello world!"
for s in str {
print(s)
}
二、 获得String的字符数量
let str = "Hello world!"
let count = str.characters.count
print(count)
改为
let str = "Hello world!"
let count = str.count
print(count)
