flask_mongoengine

from flask_mongoengine import MongoEngine

Mongoengine is a Document-Object Mapper (think ORM, but for document databases)

Easy access to database collections and enforced schema

Uses pymongo under the surface

Setup

db = MongoEngine() #Database connection data in config

db.init_app(app) # In create app factory

Config

You need to define the host, the /after the url can say the db name

class DevelopmentConfig(Config):
    DEBUG=True
    #Mongoengine Variables
    MONGODB_HOST='mongodb://[username]:[password]@ds014648.mlab.com:14648/wissen'

app.config.from_object(config[config_name])
config[config_name].init_app(app)

Making Models

Potential Field

Schema

Derive from EmbeddedDocument(embed in other docs), Document, or DynamicDocument(any fields will be saved)

from mongoengine import Document, EmbeddedDocument, StringField, IntField, FileField, EmbeddedDocumentField, ListField, BooleanField, SortedListField, DateTimeField, ReferenceField

class Profile(EmbeddedDocument):
    first = StringField(max_length=50)
    last = StringField(max_length=50)
    gender = StringField(max_length=1, choices=GENDERS)
    age = IntField()
    photo = FileField() #GridGS
    bio = StringField()
    location = StringField()

Connecting Models

EmbeddedDocumentField includes the object in the model

ReferenceField can be used to include reference ids that are lazily dereferenced on access

class User(UserMixin, Document):
    cid = ReferenceField('Connection')
    profile = EmbeddedDocumentField(Profile, required=True)
    #...

Creation

profile = Profile(first=form['first'], last=form['last'], gender=form['gender'][0], age=form['age'], bio=form['bio'], location=form['location']) 
profile.save()

An id is created automatically on save: profile.id , convert to string with str(profile.id)

Set id by adding primary_key=True to Field and it will be aliased to id

Images Add Photo

file = request.files['profile_image']
profile.photo.new_file()
profile.photo.write(file)
profile.photo.close()
profile.photo = current_user.profile.photo
current_user.profile = profile

#Save to DB
current_user.save()

Retrieve Img

img = Image.objects()[0].img.read()

Query

You need to define and import the model

#return all objects 
User.objects 
#Query in embedded docs
Page.objects(author__country='uk') 
#only first 5 people(??throw error if not exist??)
User.objects[:5] 
# retrieve first result or None if it doesnt exist
User.objects.first()
for user in User.objects(username='jfuentes'):
    print(user.email)

Operators

Double underscore after field to do operator

• in – value is in list (a list of values should be provided)

#Query users with age less or equal
Users.objects(age__lte=18)

Advanced

Page.objects(__raw__={'tags': 'coding'})

class Page(Document):
    tags = ListField(StringField())
# This will match all pages that have the word 'coding' as an item in the 'tags' list
Page.objects(tags='coding')