如何在Array#delete_if中引用元素的索引 [英] How to refer the index of an element in Array#delete_if

问题描述

我想构建一个自定义方法Array#drop_every(n)(我知道这是猴子补丁，我正在做家庭作业)，该方法将返回一个新数组，省略每个第n个元素:

I want to build a custom method Array#drop_every(n) (I know it's monkey patching, I am doing this for a homework), which returns a new array omitting every nth element:

[4, 8, 15, 16, 23, 42].drop_every(2) # [4, 15, 23]

我想用Array#delete_if实现它，但是通过引用索引而不是元素本身(类似于each_index)是这样的:

I want to implement it with Array#delete_if, but by referring to the index and not to the element itself, (similar to each_index) something like this:

def drop_every(step)
  self.delete_if { |index| index % step == 0 }
end

我该怎么做?我不坚持使用delete_if，我也查看了drop_while和reject，欢迎其他建议.

How do I do this? I don't insist on using delete_if, I also looked at drop_while and reject, other suggestions are welcome.

推荐答案

def drop_every(step)
  reject.with_index { |x,i| (i+1) % step == 0 }
end

[4, 8, 15, 16, 23, 42].reject.with_index{|x,i| (i+1) % 2 ==  0}
# => [4, 15, 23]

[4, 8, 15, 16, 23, 42].reject.with_index{|x,i| (i+1) % 3 ==  0}
# => [4, 8, 16, 23] 

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