Swift 去掉了传统的 for(int i = 0; i < nums.count; i ++) 这种写法

采用官方的示例代码

• 遍历集合

  let names = ["Anna", "Alex", "Brian", "Jack"]
  for name in names {
      print("Hello, \(name)!")
  }

• 遍历字典

  let numberOfLegs = ["spider": 8, "ant": 6, "cat": 4]
  for (animalName, legCount) in numberOfLegs {
      print("\(animalName)s have \(legCount) legs")
  }

• 便捷的遍历方式

  for index in 1...5 {
      print("\(index) times 5 is \(index * 5)")
  }

  • 如果不关心每次遍历的元素，可以忽略

    let base = 3
    let power = 10
    var answer = 1
    for _ in 1...power {
        answer *= base
    }

  • 闭区间: operator (..<)

    let minutes = 60
    for tickMark in 0..<minutes {
        // render the tick mark each minute (60 times)
    }

• 遍历的同时获取索引

  let names = ["Anna", "Alex", "Brian", "Jack"]
  for (index, name) in names.enumerated() {
      print("\(index) - Hello, \(name)!")
  }

• 还可以结合 stride(from:to:by:) 和 stride(from:through:by:) 跳过集合中的某些元素

  let minuteInterval = 5
  for tickMark in stride(from: 0, to: minutes, by: minuteInterval) {
      // render the tick mark every 5 minutes (0, 5, 10, 15 ... 45, 50, 55)
  }

  let hours = 12
  let hourInterval = 3
  for tickMark in stride(from: 3, through: hours, by: hourInterval) {
      // render the tick mark every 3 hours (3, 6, 9, 12)
  }