Ruby - 每个起始偏移量 [英] Ruby - each starting offset

问题描述

如何为 ruby​​ 中的 each 循环设置起始偏移量?我希望循环从 a[3] 而不是 a[0] 开始.我该如何设置?

How do I set a starting offset for each loop in ruby? I want the loop to begin from a[3] instead of a[0]. How do I set that?

a = [ab, cd, ef, gh, hi, jk]

a.each do |i|
#some stuff
end

推荐答案

另一种可能更直接和可读的可能性是使用 Array#drop:

Another, possibly more direct and readable possibility is to use Array#drop:

a.drop(3).each do |i|
  # do something with item i
end

现在，如果与从 Enumerable 继承的其他方法结合使用，这真的很出色，所以很有可能更好的替代命令式 each 循环.假设您要过滤提取的切片并在之后对其进行转换:

Now this really shines if combined with other methods inherited from Enumerable, so chances are there's a better alternative to your imperative each loop. Say you want to filter the extracted slice and transform it afterwards:

a = [0,1,2,3,4,5,6,7]
a.drop(3).select(&:even?).map { |x| x * 2 }
# => [8, 12]

或者说你想打印所有值的列表:

Or say you want to print a list of all the values:

a = ["1", "2", "3", "4", "5"]
puts a.drop(3).join("\n")

输出:

4
5

继承自函数式编程的这些特性使 Ruby 变得如此强大:)

These features inherited from functional programming are what makes Ruby so strong :)

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