module Liquid
# "For" iterates over an array or collection.
# Several useful variables are available to you within the loop.
#
# == Basic usage:
# {% for item in collection %}
# {{ forloop.index }}: {{ item.name }}
# {% endfor %}
#
# == Advanced usage:
# {% for item in collection %}
# <div {% if forloop.first %}class="first"{% endif %}>
# Item {{ forloop.index }}: {{ item.name }}
# </div>
# {% endfor %}
#
# You can also define a limit and offset much like SQL. Remember
# that offset starts at 0 for the first item.
#
# {% for item in collection limit:5 offset:10 %}
# {{ item.name }}
# {% end %}
#
# To reverse the for loop simply use {% for item in collection reversed %}
#
# == Available variables:
#
# forloop.name:: 'item-collection'
# forloop.length:: Length of the loop
# forloop.index:: The current item's position in the collection;
# forloop.index starts at 1.
# This is helpful for non-programmers who start believe
# the first item in an array is 1, not 0.
# forloop.index0:: The current item's position in the collection
# where the first item is 0
# forloop.rindex:: Number of items remaining in the loop
# (length - index) where 1 is the last item.
# forloop.rindex0:: Number of items remaining in the loop
# where 0 is the last item.
# forloop.first:: Returns true if the item is the first item.
# forloop.last:: Returns true if the item is the last item.
#
class For < Block
Syntax = /(\w+)\s+in\s+(#{QuotedFragment}+)\s*(reversed)?/
def initialize(tag_name, markup, tokens)
if markup =~ Syntax
@variable_name = $1
@collection_name = $2
@name = "#{$1}-#{$2}"
@reversed = $3
@attributes = {}
markup.scan(TagAttributes) do |key, value|
@attributes[key] = value
end
else
raise SyntaxError.new("Syntax Error in 'for loop' - Valid syntax: for [item] in [collection]")
end
super
end
def render(context)
context.registers[:for] ||= Hash.new(0)
collection = context[@collection_name]
collection = collection.to_a if collection.is_a?(Range)
return '' unless collection.respond_to?(:each)
from = if @attributes['offset'] == 'continue'
context.registers[:for][@name].to_i
else
context[@attributes['offset']].to_i
end
limit = context[@attributes['limit']]
to = limit ? limit.to_i + from : nil
segment = slice_collection_using_each(collection, from, to)
return '' if segment.empty?
segment.reverse! if @reversed
result = []
length = segment.length
# Store our progress through the collection for the continue flag
context.registers[:for][@name] = from + segment.length
context.stack do
segment.each_with_index do |item, index|
context[@variable_name] = item
context['forloop'] = {
'name' => @name,
'length' => length,
'index' => index + 1,
'index0' => index,
'rindex' => length - index,
'rindex0' => length - index -1,
'first' => (index == 0),
'last' => (index == length - 1) }
result << render_all(@nodelist, context)
end
end
result
end
def slice_collection_using_each(collection, from, to)
segments = []
index = 0
yielded = 0
collection.each do |item|
if to && to <= index
break
end
if from <= index
segments << item
end
index += 1
end
segments
end
end
Template.register_tag('for', For)
end
