Nested Model

Table of contents

  1. Example Usage
  2. Common mistake
  3. Deep Nested Model
    1. Filter Results
  4. Allowed Attributes
    1. Default
    2. Required
    3. Example
    4. Column Name
    5. Validator

Model inside another model.

Example Usage 

class User(Model):
    name = TextField()


class Student(Model):
    address = TextField()
    user = NestedModel(User)


u = User(name='Nested_Model')

s = Student(address="Student_address")
s.user = u
s.save()

You can also direct assign the nested_model without creating the object.

s = Student()
s.address = 'Student Address'
s.user.name = 'Azeem'  # Here you can assign without creating separate User object
s.save()

Common mistake

Don’t save the NestedModel otherwise this model will save separately.

Invalid: Don’t save the NestedModel

u = User(name='Nested_Model')
u.save()  # Don't save nested model

s = Student(address="Student_address")
s.user = u
s.save()

Deep Nested Model

There is no limit how how deep you go with nested models. You can create nested_model inside another nested_model

class Level1(Model):
    name = TextField()


class Level2(Model):
    name = TextField()
    lev1 = NestedModel(Level1)


class Level3(Model):
    name = TextField()
    lev2 = NestedModel(Level2)


l = Level3()
l.name = 'level 1'
l.lev2.name = 'level 2'
l.lev2.lev1.name = 'level 3'
l.save()

Filter Results

You can filter models with nested_models fields using dot(.) notation.

l = Level3.collection.filter('lev2.lev.name', '==', 'level 3').get()

Allowed Attributes

The following attributes supported by Nested Model.

  1. default
  2. required
  3. column_name
  4. validator

  • Default

    Default value for field. This is base attribute that is available in all fields. Read More

  • Required

    Set True if value is required for the field. This is base attribute that is available in all fields. Read More

But this behave a little different in nested models. If you set True then it will check required fields inside nested model if there is any required field and no value is given then it will give error.

Example 

class User(Model):
    name = TextField(required=True)
    age = NumberField()


class Student(Model):
    dept = TextField()
    user = NestedModel(User, required=True)

s = Student()
s.dept = 'Math'
s.user.age = 26
s.save() # ERROR! required field value is missing

If you set False in nested model then it will not check required field value is provided or not.

class Student(Model):
    dept = TextField()
    user = NestedModel(User, required=False)

s = Student()
s.dept = 'Math'
s.user.age = 26
s.save()  # Successfully saved the result without any error

  • Column Name

    Set different column name in Firestore instead of field name. This is base attribute that is available in all fields. Read More

  • Validator

    Validate given value of field. This is base attribute that is available in all fields Read More