RESTful interface in Flask and issues serializing
flask, flask-sqlalchemy, json, rest, serialization
Solution
I would use a module to do this, honestly. We've used Flask-Restless for some APIs, you might take a look at that:
https://flask-restless.readthedocs.org/en/latest/
However, if you want build your own, you can use SQLAlchemy's introspection to output your objects as key/value pairs.
http://docs.sqlalchemy.org/en/rel_0_7/core/schema.html#metadata-reflection
Something like this, although I always have to triple-check I got the syntax right, so take this as a guide more than working code.
@app.route('/tasks')
def tasks():
tasks = Tasks.query.all()
output = []
for task in tasks:
row = {}
for field in Tasks.__table__.c:
row[str(field)] = getattr(task, field, None)
output.append(row)
return jsonify(data=output)
I found this question which might help you more. I'm familiar with SQLAlchemy 0.7 and it looks like 0.8 added some nicer introspection techniques:
SQLAlchemy introspection
Problem
I'm learning Backbone.js and Flask (and Flask-sqlalchemy). I chose Flask because I read that it plays well with Backbone implementing RESTful interfaces. I'm currently following a course that uses (more or less) this model: ``` class Tasks(db.Model): id = db.Column(db.Integer, primary_key=True) title = db.Column(db.String(80), unique=True) completed = db.Column(db.Boolean, unique=False, default=False) def __init__(self, title, completed): self.title = title self.completed = completed def json_dump(self): return dict(title=self.title, completed=self.completed) def __repr__(self): return '<Task %r>' % self.title ``` I had to add a `json_dump` method in order to send JSON to the browser. Otherwise, I would get errors like `object is not JSON serializable`, so my first question is: Is there a better way to do serialization in Flask? It seems that some objects are serializable but others aren't, but in general, it's not as easy as I expected. After a while, I ended up with the following views to take care of each type of request: ``` @app.route('/tasks') def tasks(): tasks = Tasks.query.all() serialized = json.dumps([c.json_dump() for c in tasks]) return serialized @app.route('/tasks/<id>', methods=['GET']) def get_task(id): tasks = Tasks.query.get(int(id)) serialized = json.dumps(tasks.json_dump()) return serialized @app.route('/tasks/<id>', methods=['PUT']) def put_task(id): task = Tasks.query.get(int(id)) task.title = request.json['title'] task.completed = request.json['completed'] db.session.add(task) db.session.commit() serialized = json.dumps(task.json_dump()) return serialized @app.route('/tasks/<id>', methods=['DELETE']) def delete_task(id): task = Tasks.query.get(int(id)) db.session.delete(task) db.session.commit() serialized = json.dumps(task.json_dump()) return serialized @app.route('/tasks', methods=['POST']) def post_task(): task = Tasks(request.json['title'], request.json['completed']) db.session.add(task) db.session.commit() serialized = json.dumps(task.json_dump()) return serialized ``` In my opinion, it seems a bit verbose. Again, what is the proper way to implement them? I have seen some extensions that offer RESTful interfaces in Flask but those look quite complex to me. Thanks