hugo-blog/content/posts/TastyPie-Note-1.md

title	date	tags
TastyPie Note 1	2016-05-10 17:00:00	tastypie django

Flow Through The Request/Response Cycle

Tastypie can be thought of as a set of class-based view that provide the API functionality. All routing/middleware/response-handling aspectss are the same as a typical Django app. Where the differs is in the view itself.

Walking through what a GET request to a list endpoint looks like:

• The Resource.urls are checked by Django's url resolvers.

• On a match for the list view, Resource.wrap_view('dispatch_list') is called. wrap_view provides basic error handling & allows for returning serilized errors.

• Because dispatch_list was passed to wrap_view, Resource.dispatch_list is called next. This is a thin wrapper around Resource.dispatch.

• dispatch does a bunch of havy lifting. It ensures:

  • the requested HTTP method is in allowed_methos (method_check).
  • the class has a method that can handle the request(get_list)
  • the user is authenticated(is_authenticated)
  • the user has no exceeded their throttle(throttle_check).

  At this point, dispatch actually calls the requested method (get_list).

• get_list does the actual work of API. It does:

  • A fetch of the available objects via Resource.obj_get_list. In the case of ModelResource, this builds the ORM filters to apply (ModelResource.build_filters). It then gets the QuerySet via ModelResource.get_object_list (which performs Resource.authorized_read_list to possibly limit the set the user can work with) and applies the built filters to it.
  • It then sorts the objects based on user input (ModelResource.apply_sorting).
  • Then it paginates the results using the supplied Paginator & pulls out the data to be serialized.
  • The objects in the page have full_dehydrate applied to each of them, causing Tastypie to traslate the raw object data into the fields the endpoint supports.
  • Finally, it calls Resource.create_response.

• create_response is a shortcut method that:

  • Determines the desired response format (Resource.determine_format).
  • Serializes the data given to it in the proper format.
  • Returns a Django HttpResponse (200 OK) with the serialized data.

• We bubble back up the call stack to dispatch. The last thing dispatch does is potentially store that a request occured for future throttling (Resource.log_throttled_access) then either returns the HttpResponse or wraps whatever data came back in a response (so Django doesn't freak out).