Middleware engine tutorial (5) Signal

The consumer engine sends some signals when performing data operations. we can connect these signals for some additional operations. Note: To use signals in the engine, you need to install the library blinker. $ Pipinstallblinker1_engine provides the following signal: pre_init: Create a new Document or Embedded

The consumer engine sends some signals when performing data operations. we can connect these signals for some additional operations. Note: To use signals in the engine, you need to install the library blinker. $ Pip install blinker internal engine provides the following signal: pre_init: Create a new Document or Embedded

The consumer engine sends some signals when performing data operations. we can connect these signals for some additional operations. Note: To use signals in the engine, you must installBlinkerThis library.

$ pip install blinker

The signal provided by consumer engine is as follows:

• Pre_init: it is called after a new Document or EmbeddedDocument instance object is created and before the object is initialized.
• Post_init: called after the Document or EmbeddedDocument instance object initialization is complete.
• Pre_save: called before the save method is executed.
• Pre_save_post_validation: called before data is saved after data validation is complete.
• Post_save: called after the data is saved.
• Pre_delete: called before the delete method is executed.
• Post_delete: called after the record is successfully deleted.
• Pre_bulk_insert: called before data insertion after data validation.
• Post_bulk_insert: called after successful data insertion.

Event connection

Use signals to connect the signal to the callback function.

from mongoengine import *from mongoengine import signalsclass Author(Document):    name = StringField()    @classmethod    def pre_save(cls, sender, document, **kwargs):        print("Pre Save: %s" % document.name)    @classmethod    def post_save(cls, sender, document, **kwargs):        print("Post Save: %s" % document.name)        if 'created' in kwargs:            if kwargs['created']:                print("Created")            else:                print("Updated")signals.pre_save.connect(Author.pre_save, sender=Author)signals.post_save.connect(Author.post_save, sender=Author)

Note: For RefereneFieldReverse_delete_rulesParameters do not trigger signals.

Original article address: audio engine tutorial (5)-signal, thanks to the original author for sharing.