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# frozen_string_literal: true
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 liquid_method_missing(name) method which is a catch all.
class Drop
attr_writer :context
# Catch all for the method
def liquid_method_missing(method)
return nil unless @context&.strict_variables
raise Liquid::UndefinedDropMethod, "undefined method #{method}"
end
# called by liquid to invoke a drop
def invoke_drop(method_or_key)
if self.class.invokable?(method_or_key)
send(method_or_key)
else
liquid_method_missing(method_or_key)
end
end
def key?(_name)
true
end
def inspect
self.class.to_s
end
def to_liquid
self
end
def to_s
self.class.name
end
alias_method :[], :invoke_drop
# Check for method existence without invoking respond_to?, which creates symbols
def self.invokable?(method_name)
invokable_methods.include?(method_name.to_s)
end
def self.invokable_methods
@invokable_methods ||= begin
blacklist = Liquid::Drop.public_instance_methods + [:each]
if include?(Enumerable)
blacklist += Enumerable.public_instance_methods
blacklist -= [:sort, :count, :first, :min, :max]
end
whitelist = [:to_liquid] + (public_instance_methods - blacklist)
Set.new(whitelist.map(&:to_s))
end
end
end
end
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