字典

字典是一个可以用数字索引访问每个元素的集合，字典访问每个元素是通过"关键字"key

var person = ["姓氏": "周", "名字": "杰伦","职业": "歌手"]
person["姓氏"]
person["名字"]
person["职业"]

循环

使用循环语句可以在短时间内让计算机多次重复一个代码块
举例：99乘法表

for i in 1...9 {
  for u in i...9 {
    print("\(i)*\(u)=\(i*u)")
  }
}

遍历数组

var songs = ["园游会","一路向北","七里香"]
for song in songs {
  print("My favorite song is \(song)")
}

也可以使用 for i in循环遍历数组，还可以在循环内同时遍历多个数组：

var people = ["players","doctors"," teachers","workers"]
var people1 = ["play","doctor"," teacher","worker"]
for i in 0..<people.count {
  print("\(people[i]) gonna \(people1[i])")
}

循环嵌套

把一个循环放进另一个循环

var people = ["players","doctors"," teachers","workers"]
var people1 = ["play","doctor"," teacher","worker"]
for i in 0..<people.count {
  var str = "\(people[i]) gonna"
  for _ in 1...5 {
    str += "\(people1[i])"
  }
  print(str)
}

While循环

当满足条件时进入循环，进入循环后，当条件不满足时，跳出循环

var counter = 0
while true {
  print("Counter is now \(counter)")
  counter += 1
  if counter == 282 {
      break
  }
}

break:在某个条件达到时退出循环，如果没有break，循环将持续下去，成为一个无限循环。与break对应的是continue，是立刻结束此次循环并开始下一个循环。

var songs = ["园游会","一路向北","七里香"]
for song in songs {
    if song == "园游会" {
        continue
  }
    print(song)
}