feat: 增加null和not_null支持

lib/ransack_mongo/mongo_adapter.rb

 module RansackMongo
   class MongoAdapter
-    PREDICATES = %w[eq not_eq cont in start mstart gt lt gteq lteq]
+    PREDICATES = %w[null not_null eq not_eq cont in start mstart gt lt gteq lteq]
 
     def initialize
       @query = {}
@@ -10,6 +10,14 @@ module RansackMongo
       @query
     end
 
+    def null_matcher(attr, value)
+      @query[attr] = nil
+    end
+
+    def not_null_matcher(attr, value)
+      @query[attr] = { '$ne' => nil }
+    end
+
     def eq_matcher(attr, value)
       @query[attr] = value
     end

lib/ransack_mongo/predicate.rb

@@ -5,6 +5,7 @@ module RansackMongo
     end
 
     def parse(params)
+      binding.pry
       (params || {}).keys.inject({}) do |query, query_param|
         attr = query_param.to_s
         p, attr = detect_and_strip_from_string(attr)