每日一句：
不积跬步，无以至千里；不积小流，无以成江海
一、for-in循环
- 用来遍历集合类型数据（Array、Dictionary、Set）
- 遍历字符串字符也是可以的
格式：
for item in items {
code
}
事例：
//遍历数组
var nameArray = [String]()
nameArray = ["king","jone","kitty","bob","rob"]
for obj in nameArray {
print(obj)
}
for (index,obj) in nameArray.enumerated() {
print("my name is \(obj), sit at \(index)")
}
//遍历字典
var nameDic = ["name":"king","age":"100"]
for obj in nameDic {
print(obj)
}
for obj in nameDic.keys {
print(obj)
}
for obj in nameDic.values {
print(obj)
}
for (index,obj) in nameDic.enumerated() {
print("我有一个对象\(obj.key),在咖啡厅第\(index)位等我😯")
}
//遍历set
var nameSet:Set<String> = ["king","jone","kitty"]
for obj in nameSet {
print(obj)//kitty、king、jone
//从打印结果可以看出set是无序的
}
for (index,obj) in nameSet.enumerated() {
print("my name is \(obj), sit at \(index)")
}
//遍历字符串的字符
var name = "king"
for obj in name {
print(obj)//k、i、n、g
}
//遍历区间数据
for index in 1...5 {
print(index)
}
for index in 1..<5 {
print(index)
}
//从0-10，每新增1，做一件事
for obj in stride(from: 0, to: 10, by: 1) {
print("do something at \(obj)")
}
二、while循环
- while循环会一直运行一段语句直到条件变成false
- repeat-while循环，每次在循环结束时计算条件是否符合
- repeat-while和while的区别就是判断循环条件之前，先执行一次循环的代码块。
格式：
while condition {
code
}
repeat {
code
} while condition
事例：
var a = 1;
let b = 3;
while a < b {
a+=1
print(a)
}
repeat {
a-=1
print(a)
} while a>=b
三、if条件语句
事例：
if a < b {
print("maxvalue is \(b)")
}
四、switch语句
事例：
let someCharacter: Character = "z"
switch someCharacter {
case "a": break
case "z":
print("你好")
case "y": break
default:
print("hello")
}
switch someCharacter {
case "a","y": break
case "z" :
print("helloz")
default:
break
}
gitHub地址：（https://github.com/kingbroad/SwiftStudy）（欢迎👏关注❤️）
