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require 'set'
module Liquid
# A drop in liquid is a class which allows you to export DOM like things to liquid.
# Methods of drops are callable.
# The main use for liquid drops is to implement lazy loaded objects.
# If you would like to make data available to the web designers which you don't want loaded unless needed then
# a drop is a great way to do that.
#
# Example:
#
# class ProductDrop < Liquid::Drop
# def top_sales
# Shop.current.products.find(:all, :order => 'sales', :limit => 10 )
# end
# end
#
# tmpl = Liquid::Template.parse( ' {% for product in product.top_sales %} {{ product.name }} {%endfor%} ' )
# tmpl.render('product' => ProductDrop.new ) # will invoke top_sales query.
#
# Your drop can either implement the methods sans any parameters or implement the before_method(name) method which is a
# catch all.
class Drop
attr_writer :context
EMPTY_STRING = ''.freeze
# Catch all for the method
def before_method(method)
nil
end
# called by liquid to invoke a drop
def invoke_drop(method_or_key)
if method_or_key && method_or_key != EMPTY_STRING && self.class.invokable?(method_or_key)
send(method_or_key)
else
before_method(method_or_key)
end
end
def has_key?(name)
true
end
def to_liquid
self
end
alias :[] :invoke_drop
private
# Check for method existence without invoking respond_to?, which creates symbols
def self.invokable?(method_name)
@invokable_methods ||= Set.new(["to_liquid"] + (public_instance_methods - Liquid::Drop.public_instance_methods).map(&:to_s))
@invokable_methods.include?(method_name.to_s)
end
end
end
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