Swift for loop向后

Question

是否可以创建倒置Range？

我的意思是从99到1,而不是相反.我的目标是将值从99迭代到1.

这不会编译,但它应该让你知道我正在尝试做什么:

for i in 99...1{
    print("\(i) bottles of beer on the wall, \(i) bottles of beer.")
    print("Take one down and pass it around, \(i-1) bottles of beer on the wall.")
}

什么是实现这一目标的最简单方法Swift？

Answer 1

您可以使用stride(through:by:)或stride(to:by:)在任何符合Strideable协议.第一个包括列出的值,第二个在它之前停止.

例:

for i in 99.stride(through: 1, by: -1) { // creates a range of 99...1
  print("\(i) bottles of beer on the wall, \(i) bottles of beer.")
  print("Take one down and pass it around, \(i-1) bottles of beer on the wall.")
}

您还可以使用reverse():

for i in (1...99).reverse() {
  print("\(i) bottles of beer on the wall, \(i) bottles of beer.")
  print("Take one down and pass it around, \(i-1) bottles of beer on the wall.")
}