Controllers

A Controller is a normal Python class which extends from frappe.model.Document base class. This base class is the core logic of a DocType. It handles how values are loaded from the database, how they are parsed and saved back to the database.

When you create a DocType named Person, a python file is created by the name person.py and the contents look like:

import frappe
from frappe.model.document import Document

class Person(Document):
    pass

All the fields are available to the class as attributes.

Controller Methods

You can add custom methods to your Controller and it will be callable using the doc object. For example,

# controller class
class Person(Document):
    def get_full_name(self):
        """Returns the person's full name"""
        return f"{self.first_name} {self.last_name}"

# somewhere in your code
>>> doc = frappe.get_doc("Person", "000001")
>>> doc.get_full_name()
John Doe

Controller Hooks

To add custom behaviour during the lifecycle of a document, we have controller hooks.

Method Name Description Insert Save Submit Cancel Update after submit
before_insert This is called before a document is prepared for insertion. X
before_naming This is called before the name property of the document is set. X
autoname If defined in the controller, this method is used to set name property of the document. X
before_validate This hook is called before validation, use this for auto setting missing values. X X X
validate Use this method to throw any validation errors and prevent the document from saving. X X X
before_save This method is called before the document is saved. X X
before_submit This method is called before the document is submitted. X X
before_cancel This method is called before the document is cancelled. X
before_update_after_submit This method is called when doc fields are updated on submitted document. X
db_insert This method inserts document in database, do not override this unless you're working on virtual DocType. X
after_insert This is called after the document is inserted into the database. X
db_update This method updates document in database, do not override this unless you're working on virtual DocType. X X X X
on_update This is called when values of an existing document is updated. X X X
on_submit This is called when a document is submitted. X
on_cancel This is called when a submitted document is cancelled. X
on_update_after_submit This is called when a submitted document values are updated. X
on_change This is called to hen a document's values has been changed. This method is also called when db_set is performed, so operation performed in this this method should be idempotent. X X X X X

Apart from doc events for typical actions, you can also hook into other actions.

Method Name Description
before_rename This is called before a document is renamed.
after_rename This is called after a document is renamed.
on_trash This is called when a document is being deleted.
after_delete This is called after a document has been deleted.

To use a controller hook, just define a class method with that name. For e.g

class Person(Document):
    def validate(self):
        if self.age <= 18:
            frappe.throw("Person's age must be at least 18")

    def after_insert(self):
        frappe.sendmail(recipients=[self.email], message="Thank you for registering!")

You can also override the pre-defined document methods to add your own behaviour if the hooks aren't enough for you. For e.g to override the save() method,

class Person(Document):
    def save(self, *args, **kwargs):
        super().save(*args, **kwargs) # call the base save method
        do_something() # eg: trigger an API call or a Rotating File Logger that "User X has tried updating this particular record"

There are a lot of methods provided by default on the doc object. You can find the complete list here.

1. Create a document

To create a new document and save it to the database,

doc = frappe.get_doc({
    'doctype': 'Person',
    'first_name': 'John',
    'last_name': 'Doe'
})
doc.insert()

doc.name # 000001

2. Load a document

To get an existing document from the database,

doc = frappe.get_doc('Person', '000001')

# doctype fields
doc.first_name # John
doc.last_name # Doe

# standard fields
doc.creation # datetime.datetime(2018, 9, 20, 12, 39, 34, 236801)
doc.owner # john.doe@frappeframework.com

Document

A Document is an instance of a DocType. It usually maps to a single row in the database table. We refer to it as doc in code.

Example

Let's say we have a DocType ToDo with the following fields:

  • description
  • status
  • priority

Now, if we want to query a document from the database, we can use the ORM.

>>> doc = frappe.get_doc("ToDo", "0000001")
<todo: 0000001="">

>>> doc.as_dict()
{'name': '0000001',
 'owner': 'Administrator',
 'creation': datetime.datetime(2022, 3, 28, 18, 20, 23, 275229),
 'modified': datetime.datetime(2022, 3, 28, 18, 20, 23, 275229),
 'modified_by': 'Administrator',
 'docstatus': 0,
 'idx': 0,
 'status': 'Open',
 'priority': 'Medium',
 'color': None,
 'date': None,
 'allocated_to': None,
 'description': 'Test',
 'reference_type': None,
 'reference_name': None,
 'role': None,
 'assigned_by': 'Administrator',
 'assigned_by_full_name': 'Administrator',
 'sender': None,
 'assignment_rule': None,
 'doctype': 'ToDo'}

You get the values of description, status and priority, but you also get fields like creation, owner and modified_by which are fields added by default by the framework on all docs.