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module Renalware
module OrderedSetScope
extend ActiveSupport::Concern
class_methods do
# Produces a scope that orders a relation based on a attribue and the
# order of the values.
#
# @example
#
# Give the relation 'qux':
# |id | code |
# | 1 | baz |
# | 2 | bar |
# | 3 | foo |
#
# When I execute the following:
#
# Qux.fixed_order_for(:code, %i(foo bar))
#
# Then the following set is returned:
# |id | code |
# | 3 | foo |
# | 2 | bar |
#
# The implementation is based on this blog post:
# http://sqlandme.com/2013/11/18/sql-server-custom-sorting-in-order-by-clause/
#
def ordered_set(attribute, values)
verified_values = verify_values(attribute, values.map(&:to_s))
where(attribute => verified_values)
.order("CASE #{generate_conditions(attribute, values.uniq)} END")
end
private
# Verify the values exist in the database, prevents a SQL inject attack
# when ordering, as order scopes doen't sanitize.
#
def verify_values(attribute, values)
values & where(attribute => values).pluck(attribute)
end
# Example:
# Given the following:
# attribute: 'code'
# values: %w(foo bar)
# Then generates:
# WHEN code = 'foo' THEN 0
# WHEN code = 'bar' THEN 1
#
def generate_conditions(attribute, values)
values.each_with_index.map do |value, idx|
"WHEN #{attribute} = '#{value}' THEN '#{idx}'"
end.join(" ")
end
end
end
end
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28 entries across 28 versions & 1 rubygems