CODEWITHSUNDEEP
pythonjsonrestflask
Brosef
Brosef

Reputation: 3095

Flask coverting to and from JSON

I'm working on a Flask example that takes blog posts and adding them to a database through a RESTful service.

Prior to implementing the RESTful service, I was adding blog posts to a local database by doing the following: 

@main.route('/', methods=['GET', 'POST'])
def index():
    form = PostForm()
    if current_user.can(Permission.WRITE_ARTICLES) and \
            form.validate_on_submit():
        post = Post(body=form.body.data,
                    author=current_user._get_current_object())
        db.session.add(post)
        return redirect(url_for('.index'))

Now that I've gotten to the RESTful service section, the following to_json() and from_json() functions have been to the Post model:

//Convert a post from JSON
//Class Post(db.Model)
def to_json(self):
        json_post = {
            'url': url_for('api.get_post', id=self.id, _external=True),
            'body': self.body,
            'body_html': self.body_html,
            'timestamp': self.timestamp,
            'author': url_for('api.get_user', id=self.author_id,
                              _external=True),
            'comments': url_for('api_get_post_comments', id=self.id,
                                _external=True),
            'comment_count': self.comments.count()
        }
        return json_post

//Create a blog post from JSON
//Class Post(db.Model)
@staticmethod
def from_json(json_post):
    body = json_post.get('body')
    if body is None or body == '':
        raise ValidationError('post does not have a body')
    return Post(body=body)

The following inserts a new blog post in the database:

//POST resource handler for posts
@api.route('/posts/', methods=['POST'])
@permission_required(Permission.WRITE_ARTICLES)
def new_post():
    post = Post.from_json(request.json)
    post.author = g.current_user
    db.session.add(post)
    db.session.commit()
    return jsonify(post.to_json()), 201, \
        {'Location': url_for('api.get_post', id=post.id, _external=True)}

Would really appreciate it if someone could explain how these functions work with each other. My understanding of it all is that a blog post is typed up on a client device and in order to send it to the web service, the to_json function is called to convert the post to JSON. Once the web service receives the JSON version of the blog post, the from_json function is called to convert the JSON post back to its original state. Is that correct?

Edit: Just re-read the page and I think my understanding was reverse of whats actually happening. In order to get a blog post from the web service, the to_json function is called to convert the data to JSON. Then on the client side, the from_json function is called to convert the data back from JSON.

Upvotes: 1

Views: 521

Answers (1)

nivix zixer
nivix zixer

Reputation: 1651

Your edit is correct. A common response format for a REST API is JSON, which is why the the response is converted "to JSON" when returning.

Also a common header for sending data to a REST API is application/json, which is why the code converts the received data "from JSON".

Upvotes: 1

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