Class: Liquid::For

Inherits:
Block show all
Defined in:
lib/liquid/tags/for.rb

Overview

“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 %}

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.

Constant Summary collapse

Syntax = 
/(\w+)\s+in\s+(#{VariableSignature}+)/

Instance Attribute Summary

Attributes inherited from Tag

#nodelist

Instance Method Summary collapse

Methods inherited from Block

#block_delimiter, #block_name, #create_variable, #end_tag, #parse, #unknown_tag

Methods inherited from Tag

#name, #parse

Constructor Details

#initialize(tag_name, markup, tokens) ⇒ For

Returns a new instance of For.



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# File 'lib/liquid/tags/for.rb', line 45

def initialize(tag_name, markup, tokens)
  if markup =~ Syntax
    @variable_name = $1
    @collection_name = $2
    @name = "#{$1}-#{$2}"
    @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

Instance Method Details

#render(context) ⇒ Object 



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# File 'lib/liquid/tags/for.rb', line 61

def render(context)        
  context.registers[:for] ||= Hash.new(0)

  collection = context[@collection_name]
  collection = collection.to_a if collection.is_a?(Range)

  return '' if collection.nil? or collection.empty?

  range = (0..collection.length)

  if @attributes['limit'] or @attributes['offset']
    offset = 0
    if @attributes['offset'] == 'continue'
      offset = context.registers[:for][@name] 
    else          
      offset = context[@attributes['offset']] || 0
    end
    limit  = context[@attributes['limit']]

    range_end = limit ? offset + limit : collection.length
    range = (offset..range_end-1)
  
    # Save the range end in the registers so that future calls to 
    # offset:continue have something to pick up
    context.registers[:for][@name] = range_end
  end
        
  result = []
  segment = collection[range]
  return '' if segment.nil?        

  context.stack do 
    length = segment.length
  
    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

  # Store position of last element we rendered. This allows us to do 

  result 
end