Custom Field

Table of contents

1. Simple
   1. Example Usage
2. Extend DB value
   1. Example Usage
3. Extend Field Value
   1. Example Usage
4. Create attributes
   1. Method to create field attributes
   2. Example Usage

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Create your own custom fields, extend the class from base Field or you can extend any existing field also.

Simple

You can create simplest field just by extending base Field

Example Usage

class WeekDays(Field):
    pass


class User(Model):
    day = WeekDays()

u = User(day=1)
u.save()

Extend DB value

Control how the value of field will be save in Firestore. Override method db_value() to change the value.

Example Usage

class WeekDays(Field):
    days = ['Mon', 'Tue', 'Wed', 'Thu', 'Fri', 'Sat', 'Sun']

    def db_value(self, val):
        return self.days[val]

u = User(day=0)
u.save()

# This will save "Mon" instead of "0" in Firestore
print(u.day)  # Mon

Extend Field Value

Control how value represent when coming for Firestore. Override method field_value() to control this behaviour.

Example Usage

class WeekDays(Field):
    days = ['Mon', 'Tue', 'Wed', 'Thu', 'Fri', 'Sat', 'Sun']

    def db_value(self, val):
        return self.days[val]

    def field_value(self, val):
        return self.days.index(val)


u = User(day=0)
u.save()

# This will save "Mon" instead of "0" in Firestore
# But when you get value it will return "0" instead of "Mon"

user = User.collection.get(u.key)
print(user.day)  # 0

Create attributes

Default, Required and Column Name attributes are allowed in every field. But you can create more attributes for your field.

Method to create field attributes

Add filed attribute in the allowed_attributes list and then create method for each attribute. Method name must be start from attr_ and then the name of the attribute. Method should return the value otherwise None value set for field

Attribute Method run in the same order as they are specify in allowed_attributes

Example Usage

class EmailGenerator(Field):
    allowed_attributes = ['prefix', 'domain']

    def attr_prefix(self, attr_val, field_val):
        return attr_val + "." + field_val

    def attr_domain(self, attr_val, field_val):
        return field_val + "@" + attr_val


class User(Model):
    email = EmailGenerator(prefix='prefix', domain='example.com')

u = User()
u.email = 'my_email'
u.save()

# This will save email in Firestore like this "prefix.my_email@example.com"
print(u.email)  #  prefix.my_email@example.com