python - How to access information bi-directionally from a through relationship in SQLAlchemy

Question

I've created an application similar to Twitter where user's can "like" messages from other users. I am trying to get all of a particular user's messages that they "liked", to show up on a specific route. However, I am having trouble getting the message text to show up. I have created a join table, "Likes" that references information from both the "User" and "Message" table. Here is my code:

MODELS

class Likes(db.Model):
    """Mapping user likes to warbles."""

    __tablename__ = 'likes' 

    id = db.Column(
        db.Integer,
        primary_key=True
    )

    user_id = db.Column(
        db.Integer,
        db.ForeignKey('users.id', ondelete='cascade')
    )

    message_id = db.Column(
        db.Integer,
        db.ForeignKey('messages.id', ondelete='cascade'),
        unique=True
    )



class User(db.Model):
    """User in the system."""

    __tablename__ = 'users'

    id = db.Column(
        db.Integer,
        primary_key=True,
    )

    email = db.Column(
        db.Text,
        nullable=False,
        unique=True,
    )

    username = db.Column(
        db.Text,
        nullable=False,
        unique=True,
    )

    image_url = db.Column(
        db.Text,
        default="/static/images/default-pic.png",
    )

    header_image_url = db.Column(
        db.Text,
        default="/static/images/warbler-hero.jpg"
    )

    bio = db.Column(
        db.Text,
    )

    location = db.Column(
        db.Text,
    )

    password = db.Column(
        db.Text,
        nullable=False,
    )

    messages = db.relationship('Message')

    followers = db.relationship(
        "User",
        secondary="follows",
        primaryjoin=(Follows.user_being_followed_id == id),
        secondaryjoin=(Follows.user_following_id == id)
    )

    following = db.relationship(
        "User",
        secondary="follows",
        primaryjoin=(Follows.user_following_id == id),
        secondaryjoin=(Follows.user_being_followed_id == id)
    )

    likes = db.relationship(
        'Likes',
        backref='user'
    )


class Message(db.Model):
    """An individual message ("warble")."""

    __tablename__ = 'messages'

    id = db.Column(
        db.Integer,
        primary_key=True,
    )

    text = db.Column(
        db.String(140),
        nullable=False,
    )

    timestamp = db.Column(
        db.DateTime,
        nullable=False,
        default=datetime.utcnow(),
    )

    user_id = db.Column(
        db.Integer,
        db.ForeignKey('users.id', ondelete='CASCADE'),
        nullable=False,
    )

    user = db.relationship('User')
    

Here is how I am retrieving information to send to Jinja:

APP.PY

@app.route('/users/show_likes')
def show_liked_warbles():
    likes = Likes.query.all()
    return render_template('/users/show_liked_warbles.html', likes=likes)

Trying to get liked messages to show up (g.user references the current user in session)

Jinja

{% for likes in g.user.likes %}
    <h1>{{likes.message_id.text}}</h1>
{% endfor %}

From how my tables are setup, I believe that I should be able to access messages by writing, "likes.message_id.text" but nothing is appearing on the page. If I just write, "likes.message_id", id's appear, but not for text.

question from:https://stackoverflow.com/questions/65645860/how-to-access-information-bi-directionally-from-a-through-relationship-in-sqlalc

Answer 1

Waitting for answers