Create post_init method for base data layer, use it in the resource

Make resource attribute for the base data layer mandatory

Author: mahenzon

flask_rest_jsonapi/data_layers/alchemy.py

@@ -125,7 +125,7 @@ def get_object(self, view_kwargs, qs=None):
 
         query = self.retrieve_object_query(view_kwargs, filter_field, filter_value)
 
-        if hasattr(self, "resource"):
+        if self.resource is not None:
             for i_plugins in self.resource.plugins:
                 try:
                     query = i_plugins.data_layer_get_object_update_query(

flask_rest_jsonapi/data_layers/base.py

@@ -5,6 +5,10 @@
 """
 
 import types
+from typing import TYPE_CHECKING, Optional
+
+if TYPE_CHECKING:
+    from flask_rest_jsonapi.resource import Resource
 
 
 class BaseDataLayer:
@@ -38,6 +42,11 @@ def __init__(self, kwargs):
 
         :param dict kwargs: information about data layer instance
         """
+
+        # initing this attribute here in the first place
+        # because it can be easily overridden by kwargs below
+        self.resource: Optional['Resource'] = None
+
         if kwargs.get("methods") is not None:
             self.bound_rewritable_methods(kwargs["methods"])
             kwargs.pop("methods")
@@ -47,6 +56,17 @@ def __init__(self, kwargs):
         for key, value in kwargs.items():
             setattr(self, key, value)
 
+    def post_init(self):
+        """
+        Post init stage.
+
+        At this moment self.resource is already defined
+        and the layer can do any post init stuff here
+
+        NOTE that the data layer is inited for each request
+        :return:
+        """
+
     def create_object(self, data, view_kwargs):
         """Create an object
 

flask_rest_jsonapi/resource.py

@@ -55,6 +55,7 @@ def __new__(cls):
         """Constructor of a resource instance"""
         if hasattr(cls, "_data_layer"):
             cls._data_layer.resource = cls
+            cls._data_layer.post_init()
 
         return super().__new__(cls)