Describing Pluggable Views
- Pluggable views are inspired by the generic views from Django
- They are used to replace parts of implementations
- Let's use this function as an example:
>>> @app.route('/users/')
... def show_users(page):
... users = User.query.all()
... return render_template('users.html', users=users)- And convert it into a customizable view:
>>> from flask.views import View
>>> class ListView(View):
... def get_template_name(self):
... raise NotImplementedError()
... def dispatch_request(self):
... context = {'objects': self.get_objects()}
... return render_template(context)
>>> class UserView(ListView):
... def get_template_name(self):
... return 'users.html'
... def get_objects(self):
... return User.query.all()Method Based Dispatching
- Executing a different function for each HTTP method is useful for RESTful APIs
- We can do this with
flask.views.MethodView - Each HTTP method maps to a function with the same name
- As a result, we don't need to provide the
methodsattribute - The following is an example:
>>> from flask.views import MethodView
>>> class UserAPI(MethodView):
... def get(self):
... users = User.query.all()
... def post(self):
... user = User.from_form_data(request.form)
>>> api_func = UserAPI.as_view('users')
>>> app.add_url_rule('/users/', view_func=api_func)Method Views for APIs
- Suppose we're exposing a user object on the web
- Then, we want the user to inherit the following behavior:
| URL | Method | Description |
|---|---|---|
/users/ |
GET |
Gives a list of all users |
/users/ |
POST |
Creates a new user |
/users/<id> |
GET |
Shows a single user |
/users/<id> |
PUT |
Updates a single user |
/users/<id> |
DELETE |
Deletes a single user |
- We could do this nicely using
MethodView - The following is an example:
>>> class UserAPI(MethodView):
>>> def get(self, user_id):
... if user_id is None:
... # return a list of users
... pass
... else:
... # expose a single user
... pass
... def post(self):
... # create a new user
... pass
... def delete(self, user_id):
... # delete a single user
... pass
... def put(self, user_id):
... # update a single user
... pass- Now, the routing system can be set up like:
>>> user_view = UserAPI.as_view('user_api')
>>> # GET behavior
>>> app.add_url_rule('/users/',
... defaults={'user_id': None},
... view_func=user_view,
... methods=['GET',])
>>> # POST behavior
>>> app.add_url_rule('/users/',
... view_func=user_view,
... methods=['POST',])
>>> # Other behavior
>>> app.add_url_rule('/users/<int:user_id>',
... view_func=user_view,
... methods=['GET', 'PUT', 'DELETE'])References
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