From 92a603387c084f13a36bbf3844d89029bb73a753 Mon Sep 17 00:00:00 2001
From: sgrif <sean@thoughtbot.com>
Date: Fri, 17 May 2013 18:23:57 -0600
Subject: Add ability to specify how a class is converted to Arel predicate

This adds the ability for rails apps or gems to have granular control
over how a domain object is converted to sql. One simple use case would
be to add support for Regexp. Another simple case would be something
like the following:

    class DateRange < Struct.new(:start, :end)
      def include?(date)
        (start..end).cover?(date)
      end
    end

    class DateRangePredicate
      def call(attribute, range)
        attribute.in(range.start..range.end)
      end
    end

    ActiveRecord::PredicateBuilder.register_handler(DateRange,
      DateRangePredicate.new)

More complex cases might include taking a currency object and converting
it from EUR to USD before performing the query.

By moving the existing handlers to this format, we were also able to
nicely refactor a rather nasty method in PredicateBuilder.
---
 .../relation/predicate_builder/relation_handler.rb          | 13 +++++++++++++
 1 file changed, 13 insertions(+)
 create mode 100644 activerecord/lib/active_record/relation/predicate_builder/relation_handler.rb

(limited to 'activerecord/lib/active_record/relation/predicate_builder/relation_handler.rb')

diff --git a/activerecord/lib/active_record/relation/predicate_builder/relation_handler.rb b/activerecord/lib/active_record/relation/predicate_builder/relation_handler.rb
new file mode 100644
index 0000000000..618fa3cdd9
--- /dev/null
+++ b/activerecord/lib/active_record/relation/predicate_builder/relation_handler.rb
@@ -0,0 +1,13 @@
+module ActiveRecord
+  class PredicateBuilder
+    class RelationHandler # :nodoc:
+      def call(attribute, value)
+        if value.select_values.empty?
+          value = value.select(value.klass.arel_table[value.klass.primary_key])
+        end
+
+        attribute.in(value.arel.ast)
+      end
+    end
+  end
+end
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