class Liquid::For
“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> {% else %} There is nothing in the collection. {% 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 %} (note that the flag's spelling is different to the filter `reverse`)
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.
- forloop.parentloop
-
Provides access to the parent loop, if present.
Constants
- Syntax
Attributes
Public Class Methods
Liquid::Block::new
# File lib/liquid/tags/for.rb, line 53 def initialize(tag_name, markup, options) super @from = @limit = nil parse_with_selected_parser(markup) @for_block = new_body @else_block = nil end
Public Instance Methods
# File lib/liquid/tags/for.rb, line 73 def nodelist @else_block ? [@for_block, @else_block] : [@for_block] end
# File lib/liquid/tags/for.rb, line 61 def parse(tokens) if parse_body(@for_block, tokens) parse_body(@else_block, tokens) end if blank? @else_block&.remove_blank_strings @for_block.remove_blank_strings end @else_block&.freeze @for_block.freeze end
# File lib/liquid/tags/for.rb, line 82 def render_to_output_buffer(context, output) segment = collection_segment(context) if segment.empty? render_else(context, output) else render_segment(context, output, segment) end output end
Liquid::Block#unknown_tag
# File lib/liquid/tags/for.rb, line 77 def unknown_tag(tag, markup, tokens) return super unless tag == 'else' @else_block = new_body end
Protected Instance Methods
# File lib/liquid/tags/for.rb, line 96 def lax_parse(markup) if markup =~ Syntax @variable_name = Regexp.last_match(1) collection_name = Regexp.last_match(2) @reversed = !!Regexp.last_match(3) @name = "#{@variable_name}-#{collection_name}" @collection_name = parse_expression(collection_name) markup.scan(TagAttributes) do |key, value| set_attribute(key, value) end else raise SyntaxError, options[:locale].t("errors.syntax.for") end end
# File lib/liquid/tags/for.rb, line 111 def strict_parse(markup) p = Parser.new(markup) @variable_name = p.consume(:id) raise SyntaxError, options[:locale].t("errors.syntax.for_invalid_in") unless p.id?('in') collection_name = p.expression @collection_name = parse_expression(collection_name) @name = "#{@variable_name}-#{collection_name}" @reversed = p.id?('reversed') while p.look(:id) && p.look(:colon, 1) unless (attribute = p.id?('limit') || p.id?('offset')) raise SyntaxError, options[:locale].t("errors.syntax.for_invalid_attribute") end p.consume set_attribute(attribute, p.expression) end p.consume(:end_of_string) end
Private Instance Methods
# File lib/liquid/tags/for.rb, line 134 def collection_segment(context) offsets = context.registers[:for] ||= {} from = if @from == :continue offsets[@name].to_i else from_value = context.evaluate(@from) if from_value.nil? 0 else Utils.to_integer(from_value) end end collection = context.evaluate(@collection_name) collection = collection.to_a if collection.is_a?(Range) limit_value = context.evaluate(@limit) to = if limit_value.nil? nil else Utils.to_integer(limit_value) + from end segment = Utils.slice_collection(collection, from, to) segment.reverse! if @reversed offsets[@name] = from + segment.length segment end
# File lib/liquid/tags/for.rb, line 211 def render_else(context, output) if @else_block @else_block.render_to_output_buffer(context, output) else output end end
# File lib/liquid/tags/for.rb, line 166 def render_segment(context, output, segment) for_stack = context.registers[:for_stack] ||= [] length = segment.length context.stack do loop_vars = Liquid::ForloopDrop.new(@name, length, for_stack[-1]) for_stack.push(loop_vars) begin context['forloop'] = loop_vars segment.each do |item| context[@variable_name] = item @for_block.render_to_output_buffer(context, output) loop_vars.send(:increment!) # Handle any interrupts if they exist. next unless context.interrupt? interrupt = context.pop_interrupt break if interrupt.is_a?(BreakInterrupt) next if interrupt.is_a?(ContinueInterrupt) end ensure for_stack.pop end end output end
# File lib/liquid/tags/for.rb, line 197 def set_attribute(key, expr) case key when 'offset' @from = if expr == 'continue' Usage.increment('for_offset_continue') :continue else parse_expression(expr) end when 'limit' @limit = parse_expression(expr) end end