arel_predicate can be a proc...

...accepting typecasted, but yet unformatted, value

lib/ransack/configuration.rb

@@ -20,7 +20,6 @@ module Ransack
       compounds = opts.delete(:compounds)
       compounds = true if compounds.nil?
       compounds = false if opts[:wants_array]
-      opts[:arel_predicate] = opts[:arel_predicate].to_s
 
       self.predicates[name] = Predicate.new(opts)
 
@@ -28,7 +27,7 @@ module Ransack
         self.predicates[name + suffix] = Predicate.new(
           opts.merge(
             :name => name + suffix,
-            :arel_predicate => opts[:arel_predicate] + suffix,
+            :arel_predicate => arel_predicate_with_suffix(opts[:arel_predicate], suffix),
             :compound => true
           )
         )
@@ -40,5 +39,13 @@ module Ransack
       self.options[:search_key] = name
     end
 
+    def arel_predicate_with_suffix arel_predicate, suffix
+      case arel_predicate
+      when Proc
+        proc { |v| arel_predicate.call(v).to_s + suffix }
+      else
+        arel_predicate.to_s + suffix
+      end
+    end
   end
 end

lib/ransack/nodes/condition.rb

@@ -169,7 +169,7 @@ module Ransack
       def arel_predicate
         predicates = attributes.map do |attr|
           attr.attr.send(
-            predicate.arel_predicate, formatted_values_for_attribute(attr)
+            arel_predicate_for_attribute(attr), formatted_values_for_attribute(attr)
             )
         end
 
@@ -203,6 +203,17 @@ module Ransack
         predicate.wants_array ? formatted : formatted.first
       end
 
+      def arel_predicate_for_attribute attr
+        case predicate.arel_predicate
+        when Proc
+          values = casted_values_for_attribute(attr)
+          predicate.arel_predicate.call(predicate.wants_array ? values : values.first)
+        else
+          predicate.arel_predicate
+        end
+      end
+
+
       def default_type
         predicate.type || (attributes.first && attributes.first.type)
       end