model.py

from flask_sqlalchemy import SQLAlchemy


db = SQLAlchemy()


class Melon(db.Model):
    """Melon"""

    __tablename__ = 'melons'

    melon_code = db.Column(db.String(8), primary_key=True)
    name = db.Column(db.String, nullable=False)
    price = db.Column(db.Float, nullable=False)
    image_url = db.Column(db.String, nullable=False)
    color = db.Column(db.String, nullable=False)
    seedless = db.Column(db.Boolean, nullable=False)

    melon_type_id = db.Column(db.Integer, db.ForeignKey('types.type_id'))

    melon_type = db.relationship('MelonType', back_populates='melons')

    def __repr__(self):
        return f'<Melon melon_code={self.melon_code}>'

    def to_dict(self):
        return {'melon_code': self.melon_code,
                'name': self.name,
                'price': self.price,
                'image_url': self.image_url,
                'color': self.color,
                'seedless': self.seedless,
                'melon_type': self.melon_type.name}


class MelonType(db.Model):
    """Type of melon."""

    __tablename__ = 'types'

    type_id = db.Column(db.Integer, autoincrement=True, primary_key=True)
    name = db.Column(db.String, nullable=False)

    melons = db.relationship('Melon', back_populates='melon_type')


    def __repr__(self):
        return f'<MelonType name={self.name}>'

    def to_dict(self):
        return {'type_id': self.type_id,
                'name': self.name}


def connect_to_db(app):

    app.config['SQLALCHEMY_DATABASE_URI'] = 'postgresql:///melons'
    app.config['SQLALCHEMY_TRACK_MODIFICATIONS'] = False
    app.config['SQLALCHEMY_ECHO'] = True

    db.app = app
    db.init_app(app)

    print('Connected to database!')


if __name__ == '__main__':
    from server import app

    connect_to_db(app)