I have a model, say, Ticket. The Ticket has Tag as ManyToMany field among the other fields.
After somebody updates any field of Ticket (say Description), I want to set the Tag field value to one of the existing tags.
How do I do this?
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vignz.pie
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1 Answers
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Use Django signals
@receiver(post_save, sender=Ticket)
def create_tag(sender, instance, created, **kwargs):
if not created:
instance.tags.add(Tag.objects.get(id=1)) #Add an existing tag
instance.save()
post_save.connect(create_tag, sender=Ticket)
Mohit Harshan
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Why are you suggesting to add tag only if `created` is `True`? – vignz.pie Feb 25 '19 at 11:48
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tag is a manytomany field inside Ticket .. Why do you want to add tag without a Ticket instance? If you remove created also the code will run,just a more organised way to do it – Mohit Harshan Feb 25 '19 at 11:49
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Can't we add a tag on update of Ticket? I believe created is true if it is a newly created ticket, correct me! – vignz.pie Feb 25 '19 at 11:50
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I edited my answer..ALso post_save would be called if .save() is called. Does not get called on .update() – Mohit Harshan Feb 25 '19 at 11:56
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Is there any to avoid infinite recursion caused by calling .save() wihtin post_save? – vignz.pie Feb 25 '19 at 12:11
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https://stackoverflow.com/questions/10840030/django-post-save-preventing-recursion-without-overriding-model-save @vignz.pie – Mohit Harshan Feb 25 '19 at 12:13