Inspired by the Liquid templating language’s nice for loop goodies, each_with_context provides some contextual information about an element in an each loop.
If you’ve ever found yourself writing an each_with_index and checking i == 0 to see if the element is the first, or wondering whether the next element is differs from the current, this gem is for you.
To use, just install the gem:
sudo gem install bkoski-each_with_context --source http://gems.github.com
and
require 'each_with_context'
Now you can call each_with_context on anything that’s already Enumerable.
each_with_context accepts a block with two params: the element, and an EnumerableContext describing the element. For example:
[1,2,3].each_with_context do |num, context| # Here, you can call: context.first? # true if num is first element context.last? # true if num is last element context.edge # returns :first if first?, :last if last?, nil otherwise # useful when determining CSS selectors context.next # next element; nil if that doesn't exist context.previous # previous element; nil if that doesn't exist context.next_differs_on?(:some-method) # These methods return true if element.some_method != next/previous.some_method context.previous_differs_on?(:some-method) # If there is no next/previous, they return nil context.previous_is? {|element, previous_element| previous_element > element} # These methods yield element and next/previous, then return the result of the block context.next_is? {|element, next_element| next_element * 2 == element} # Useful for more advanced comparisons. Method returns nil if there is no next/previous. end
Copyright © 2009 Ben Koski. See LICENSE for details.