How to access the parent collection in a each closure?

问题

I'm looking from something that to replace the *parent*.

%w[apple apples].each do |w|
   next if *parent*.includes? w + "s"
   puts w
end

# output: apples

回答1:

each is a convention, there is no concept of a "parent collection" for blocks in general or ones passed to each in particular. Just name it, eg

(parent = %w[apple apples]).each do |w|
  next if parent.includes? w + "s"
  puts w
end

You could add a different method to pass a parent,

eg

module Each2
 def each2
   each { |elem| yield(self, elem) }
 end
end

include Each2

%w[apple apples].each2 do |parent, w|
  next if parent.includes? w + "s"
  puts w
end

But this is pretty silly.

回答2:

There's no way to do that. You'll have to give the collection a name first:

fruits = %w[apple apples]
fruits.each do |w|
   next if fruits.includes? w + "s"
   puts w
end

来源：https://stackoverflow.com/questions/3695789/how-to-access-the-parent-collection-in-a-each-closure