model class name should be shought from the set_model_class method first

Author: M. Saiqul Haq

README.md

@@ -87,6 +87,7 @@ end
 * For `paginator options`, just uncomment the paginator you would like to use, given
 the gems bundled in your project. For example, if your models are using `Kaminari`, uncomment `AjaxDatatablesRails::Extensions::Kaminari`. You may remove all commented lines.
   * `SimplePaginator` is the most basic of them all, it falls back to passing `offset` and `limit` at the database level (through `ActiveRecord` of course, as that is the only ORM supported for the time being).
+
 * For `sortable_columns`, assign an array of the database columns that correspond to the columns in our view table. For example `[users.f_name, users.l_name, users.bio]`. This array is used for sorting by various columns.
 
 * For `searchable_columns`, assign an array of the database columns that you want searchable by datatables. For example `[users.f_name, users.l_name]`

lib/ajax-datatables-rails/base.rb

@@ -21,7 +21,7 @@ def setup
     end
 
     def models
-      @models
+      @models ||= AjaxDatatablesRails::Models.new
     end
 
     def config
@@ -117,8 +117,8 @@ def build_conditions_for(query)
 
     def search_condition(column, value)
       model, column = column.split('.')
-      model_class = model.singularize.titleize.gsub( / /, '' ).safe_constantize
-      model_class = models[model] if model_class.nil?
+      model_class = models[model]
+      model_class = model.singularize.titleize.gsub( / /, '' ).safe_constantize if model_class.nil?
       raise("Model with class name #{model} not found") if model_class.nil?
 
       casted_column = ::Arel::Nodes::NamedFunction.new('CAST', [model_class.arel_table[column.to_sym].as(typecast)])