Ruby: Yield within enumerable

Question

I'd like to be able to yield within an enumerable block, in order to create some boilerplate benchmarking code.

Basically I'd like to do something this (simplified):

def iterator( enumerable, &block )
  iterations = enumerable.size
  counter = 0
  enumerable.each do |item|
    counter +=1
    puts "Iterating #{counter}/#{iterations}..."
    yield
  end
end

Then I'd like to be able to use this method in order to wrap this boilerplate benchmarking code around a block I would be iterating, so that I could call something like:

# assuming foo is an enumerable collection of objects
iterator foo do
  item.slow_method
  item.mundane_method
  item.save
end

... and when this code executed I would get the following log output:

Iterating 1/1234...
Iterating 2/1234...
Iterating 3/1234...

It seems like this kind of thing must be possible, but I haven't been able to figure out the syntax, nor what such a thing is called (in order to look it up).

The problem is I need to wrap boilerplate both OUTSIDE the enumerable object that is going to iterate, and also INSIDE the iteration block. I can pass an enumerable object in just fine, but I can't seem to call methods on the iterated objects from within the block I pass in.

I hope this explanation makes sense, I'm having a hard time describing it. Please leave comments if you need clarification on anything, I'll try to explain better.

You may want to use `enumerable.zip(1..size).each do |item, counter|` for "cleaner" looking code. — Andrew Grimm, Aug 01 '11 at 00:04

Ray Toal · Accepted Answer · 2011-07-30T00:21:30.600

Ruby's yield statement can take arguments. You would want to say

yield item

This passes the "current" item to your "outside" block.

Hope I understood the question correctly.

ADDENDUM

And here is the code to show it in action:

class Item
  def initialize(id)
    @id = id
  end
  def slow_method()
    puts "slow #@id"
  end
  def mundane_method()
    puts "mundane #@id"
  end
  def save()
    puts "save #@id"
  end
end

foo = [Item.new(100), Item.new(200), Item.new(300)]

def iterator(enumerable, &block)
  iterations = enumerable.size
  counter = 0
  enumerable.each do |item|
    counter +=1
    puts "Iterating #{counter}/#{iterations}..."
    yield item
  end
end

iterator foo do |item|
  item.slow_method
  item.mundane_method
  item.save
end

Ruby: Yield within enumerable

1 Answers1