backend/app.py

app.py

from flask import Flask, render_template, jsonify, request
from config import Config
from flask_sqlalchemy import SQLAlchemy
from flask_restful import Resource, Api
from flask_cors import CORS
# https://flask-marshmallow.readthedocs.io/en/latest/
from flask_marshmallow import Marshmallow
import os


# https://flaskvuejs.herokuapp.com/sqlalchemy
app = Flask(__name__)
CORS(app)
# load settings from the config.py
app.config.from_object(Config)
# for RESTful api
api = Api(app)
#  init db object
db = SQLAlchemy(app)
# marshmallow converting complex datatypes, such as objects, to and from native Python datatypes
ma = Marshmallow(app)

# Create the database model  https://www.lucidchart.com/pages/database-diagram/database-design#discovery__top
# logical structure of a database and manner data can be stored, organized and manipulated. 
class Todo(db.Model):
    # Use Column to define a column. 
    id = db.Column('todo_id', db.Integer, primary_key=True)
    content = db.Column(db.String)
    done = db.Column(db.Boolean)
    # def __init__ is optional: 
    # SQLAlchemy adds an implicit constructor to accept keyword arguments for all its columns and relationships

# Integration with Flask-SQLAlchemy and marshmallow-sqlalchemy
# ModelSchema that generates fields based on the model class Meta option
class TodoSchema(ma.ModelSchema):
    # class Meta options are a way to configure and modify a Schema's behavior. 
    class Meta:
        model = Todo

# if the database does not exist, use db.create_all()
def initialize_database():
    try:
        Todo.query.get(1)
    except:
        db.create_all()
        # put some place holder data
        todo1 = Todo(content='buy food', done=False)
        todo2 = Todo(content='cook food', done=False)
        # add and then commit to apply changes
        db.session.add(todo1)
        db.session.add(todo2)
        db.session.commit()
        # delete use: db.session.delete(me)

def query_database():
    todos = Todo.query.all()
    todos_schema = TodoSchema(many=True)
    # convert the sqlresult into python dictionary that can be jsonify
    output = todos_schema.dump(todos).data
    return output

def modify_todo( id=-1, content='', done=False, delete=False):
    if id == -1:
        # if the id is not specified, then we add a new item
        new_todo = Todo(content=content, done=done)
        db.session.add(new_todo)
    else:
        # if the id already exist, then modify the existing item
        existing_todo = Todo.query.get(id)
        if delete == True:
            db.session.delete(existing_todo)
        else:
            existing_todo.content = content
            existing_todo.done = done

    # apply changes
    db.session.commit()

class todo_database_access(Resource):
    def get(self):
        # the arguments for the function is given by the URL
        # curl http://localhost:5000
        output = query_database()
        return jsonify(output)
    def post(self):
        # curl http://localhost:5000/ -d "data=wassup" -X POST -v
        # accept argument by parsing the packages
        # todo_args = parser.parse_args()
        # todo_args = request.get_json()['todo_args']
        todo_args = request.get_json()
        print(todo_args)
        modify_todo(**todo_args)
        return jsonify(status='modify success')

api.add_resource(todo_database_access, '/todo_db')

if __name__ == '__main__':
    initialize_database()
    query_database()
    app.run(debug=True)