each_with_context

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.

INSTALLATION

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.

USAGE

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

Copyright © 2009 Ben Koski. See LICENSE for details.