Hi everyone, Does anyone know how to post blog at below page: https://www.djangoproject.com/community/blogs/
I am really frustrated as I submitted last week but nothing is there. Who is in charge of blog posts on Django site? Thx, Matt On Thu, Jul 25, 2019 at 12:38 AM Mike Dewhirst <[email protected]> wrote: > On 25/07/2019 1:03 pm, Jim Illback wrote: > > I had a slight variation on this thread - where to put some M2M field > > validation/deletion logic. > > > > I have a purely model-based form where a checkbox’s value determines > > whether another field (it’s a M2M field) in the form should be NULL or > > keep its values to be saved in the database. So, following the > > appropriate separation of concerns as advocated below, I added logic > > in both the models' clean and save override methods. Neither approach > > set the other field to NULL when it should have been. The reason is > > the form still contained M2M values even though the model said to > > delete them (delete the set, actually). > > > > After a lot of trial and error, it turns out that the model’s save > > seems to be run BEFORE the form’s save. To me, that seems backwards. > > Shouldn’t the model’s processes (which are directly relate to the > > database, the ultimate data source) occur last and well before the > > form’s (which are merely an interaction with the user)? What was > > happening was my model’s delete actually did the deletions (those IDs > > were gone), but then the form’s processing came along afterwards and > > re-inserted them again (with brand new IDs). > > Don't know what's happening here but you can be sure Django is doing it > the right way. > > Maybe you need to look at your on_delete constants. models.CASCADE > versus models.SET_NULL or models.PROTECT > > > > > Can someone help me understand why Django has chosen this seemingly > > “inversion” of processing - first models’ processes, then forms’? And, > > perhaps more importantly, where should this either/or logic should be > > placed so it will take effect? > > > > Thanks very much, > > Jim Illback > > > >> On Jul 13, 2019, at 11:48 PM, Mike Dewhirst <[email protected] > >> <mailto:[email protected]>> wrote: > >> > >> Well yes it could be called multifaceted. > >> > >> Usually but not always the interface with the user is the form. You > >> can have non-database fields as well as model fields so either way > >> there has to be a full suite of validation functionality available in > >> both types of forms. Luckily, model forms automatically call > >> model.clean() for you. > >> > >> Unit tests don't though. You have deliberately call obj.clean() if > >> you want to test things. obj.save() doesn't call obj.clean(). > >> > >> Actually, I also do a bit in view code too especially if there are > >> non-database or hidden fields in the form. I know you are not > >> supposed to validate data in a view for proper separation of concerns > >> but it does keep my forms neater. > >> > >> The bottom line for me is that if I can imagine non-form access ... > >> eg through an API ... then all validation possible has to be via > >> model.clean() and the API has to remember to call clean() before > >> saving every time there is a POST > >> > >> Hence I*always*put business rules validation in model.clean() and > >> leave 'local' validation for the form. > >> > >> You are right. There are quite a few moving parts<ic_list_happy.png> > >> > >> /Connected by Motorola/ > >> > >> > >> Dean Karres <[email protected] <mailto:[email protected]>> > wrote: > >> > >> Thank you. There are way more parts to this than I would have imagined. > >> > >> > >> > >> On Sat, Jul 13, 2019, 8:01 PM Mike Dewhirst <[email protected] > >> <mailto:[email protected]>> wrote: > >> > >> On 14/07/2019 10:37 am, Dean Karres wrote: > >>> Hi, > >>> > >>> I am learning Django. I am using CBVs. My default "index.py" > >>> view is basically a dashboard for the app I am playing with. As > >>> my models and views become more complicated I want to be able to > >>> ask, for any model instance, is this instance "valid" or > >>> "complete". Valid means that all Required elements are present > >>> and have reasonable values. "Complete" means that an instance > >>> is "valid" but also some specific bits of additional info are > >>> also ok. > >>> > >>> For example I have a Student model that has name and address > >>> info. There is a ManyToMany relation to the Class(es) in which > >>> that Student is enrolled. A "student" instance is valid if the > >>> name and address fields are filled. A student is "complete" if > >>> the student is valid and has signed up for one or more classes. > >>> > >>> So, my question is: where should the valid and complete methods > >>> live? Should they be in the Student model or CBV? Someplace > >>> else? Does it matter? > >> > >> I like to put that sort of stuff into model methods then add > >> model.clean() to call them and raise whatever error may be > >> appropriate if they fail. > >> > >> > https://docs.djangoproject.com/en/2.1/topics/forms/modelforms/#interaction-with-model-validation > >> > >> and > >> > >> > https://docs.djangoproject.com/en/2.1/ref/models/instances/#validating-objects > >> > >> and > >> > >> > https://docs.djangoproject.com/en/2.1/ref/models/instances/#django.db.models.Model.clean > >> > >> You can raise your own errors which inherit from ValidationError > >> to fine tune the process. For example, I differentiate between > >> BusinessRuleViolation and InvalidToken and a couple of others > >> where that delivers better control. > >> > >> > >>> > >>> Cheers > >>> -- > >>> You received this message because you are subscribed to the > >>> Google Groups "Django users" group. > >>> To unsubscribe from this group and stop receiving emails from > >>> it, send an email [email protected] > >>> <mailto:[email protected]>. > >>> To post to this group, send email > >>> [email protected] > >>> <mailto:[email protected]>. > >>> Visit this group athttps://groups.google.com/group/django-users. > >>> To view this discussion on the web > >>> visithttps:// > groups.google.com/d/msgid/django-users/22801669-96ec-4a43-a264-fd50c2544604%40googlegroups.com > >>> < > https://groups.google.com/d/msgid/django-users/22801669-96ec-4a43-a264-fd50c2544604%40googlegroups.com?utm_medium=email&utm_source=footer > >. > >>> For more options, visithttps://groups.google.com/d/optout. > >> > >> > >> -- > >> You received this message because you are subscribed to the Google > >> Groups "Django users" group. > >> To unsubscribe from this group and stop receiving emails from it, > >> send an email [email protected] > >> <mailto:[email protected]>. > >> To post to this group, send email [email protected] > >> <mailto:[email protected]>. > >> Visit this group athttps://groups.google.com/group/django-users. > >> To view this discussion on the web > >> visithttps:// > groups.google.com/d/msgid/django-users/ajujeafh6d4qa4vvpfv2bxf9.1563085360028%40email.android.com > >> < > https://groups.google.com/d/msgid/django-users/ajujeafh6d4qa4vvpfv2bxf9.1563085360028%40email.android.com?utm_medium=email&utm_source=footer > >. > >> For more options, visithttps://groups.google.com/d/optout. > > > > -- > > You received this message because you are subscribed to the Google > > Groups "Django users" group. > > To unsubscribe from this group and stop receiving emails from it, send > > an email to [email protected] > > <mailto:[email protected]>. > > To view this discussion on the web visit > > > https://groups.google.com/d/msgid/django-users/A2531CD5-E89E-4EB3-84C5-CF6CEB05E53D%40hotmail.com > > < > https://groups.google.com/d/msgid/django-users/A2531CD5-E89E-4EB3-84C5-CF6CEB05E53D%40hotmail.com?utm_medium=email&utm_source=footer > >. > > -- > You received this message because you are subscribed to the Google Groups > "Django users" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to [email protected]. > To view this discussion on the web visit > https://groups.google.com/d/msgid/django-users/485bb1ee-db33-09d3-a3d9-aebf337ade20%40dewhirst.com.au > . > -- Cheers, Matt Zand Cell: 202-420-9192 Work: 240-200-6131 High School Technology Services <https://myhsts.org/> DC Web Makers <https://dcwebmakers.com/> Coding Bootcamps <https://coding-bootcamps.com/> -- You received this message because you are subscribed to the Google Groups "Django users" group. 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