Re: [Django] #14969: To have a way to modify third part model classes

[Django]

#14969: To have a way to modify third part model classes
---+
  Reporter:  marinho   | Owner:  nobody
Status:  closed| Milestone:
 Component:  Database layer (models, ORM)  |   Version:  SVN   
Resolution:  wontfix   |  Keywords:
 Stage:  Unreviewed| Has_patch:  0 
Needs_docs:  0 |   Needs_tests:  0 
Needs_better_patch:  0 |  
---+
Comment (by schinckel):

 If you really feel the need to MonkeyPatch (and sometimes, it is
 unavoidable), then just use `Model.add_to_class`.

 You can even do this to modify contrib apps' models (for instance, I use
 it to add a field to `Group`, so I can have a hierarchy of groups).

 Just make sure you are very careful with your patching (ie, check to see
 if the field/attribute/method already exists on the model class, for
 instance). And be aware that you may break things.

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Re: [Django] #14969: To have a way to modify third part model classes

[Django]

#14969: To have a way to modify third part model classes
---+
  Reporter:  marinho   | Owner:  nobody
Status:  closed| Milestone:
 Component:  Database layer (models, ORM)  |   Version:  SVN   
Resolution:  wontfix   |  Keywords:
 Stage:  Unreviewed| Has_patch:  0 
Needs_docs:  0 |   Needs_tests:  0 
Needs_better_patch:  0 |  
---+
Comment (by marinho):

 Replying to [comment:4 lrekucki]:
 > Note that Russell didn't said that contrib.auth does it the right way.
 Take a look at how contrib.comments - it's not perfect, but far better. As
 for your tag example, you should take a look at [https://github.com/alex
 /django-taggit/blob/master/docs/custom_tagging.txt django-taggit] - it
 handles custom Tag models pretty well without monkey patching.

 I disagree, but as I said, I just give up.

 > From a brief review of your code, this doesn't need any change in Django
 to work, so you could just make a 3rd party application out if it.

 Yes, it is already part of django-plus.

 > PS. Writing in bold doesn't help convincing other people.

 Pointless ;)

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Re: [Django] #14969: To have a way to modify third part model classes

[Django]

#14969: To have a way to modify third part model classes
---+
  Reporter:  marinho   | Owner:  nobody
Status:  closed| Milestone:
 Component:  Database layer (models, ORM)  |   Version:  SVN   
Resolution:  wontfix   |  Keywords:
 Stage:  Unreviewed| Has_patch:  0 
Needs_docs:  0 |   Needs_tests:  0 
Needs_better_patch:  0 |  
---+
Changes (by lrekucki):

  * status:  reopened => closed
  * resolution:  => wontfix

Comment:

 Note that Russell didn't said that contrib.auth does it the right way.
 Take a look at how contrib.comments - it's not perfect, but far better. As
 for your tag example, you should take a look at [https://github.com/alex
 /django-taggit/blob/master/docs/custom_tagging.txt django-taggit] - it
 handles custom Tag models pretty well without monkey patching.

 From a brief review of your code, this doesn't need any change in Django
 to work, so you could just make a 3rd party application out if it.

 PS. Writing in bold doesn't help convincing other people.

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Re: [Django] #14969: To have a way to modify third part model classes

[Django]

#14969: To have a way to modify third part model classes
---+
  Reporter:  marinho   | Owner:  nobody
Status:  reopened  | Milestone:
 Component:  Database layer (models, ORM)  |   Version:  SVN   
Resolution:|  Keywords:
 Stage:  Unreviewed| Has_patch:  0 
Needs_docs:  0 |   Needs_tests:  0 
Needs_better_patch:  0 |  
---+
Changes (by marinho):

  * status:  closed => reopened
  * resolution:  wontfix =>

Comment:

 Replying to [comment:2 russellm]:

 Russel, I disagree to you. It would be a monkey patch if it was just a
 work around to fix something and just that.

 '''I reopen the ticket just to ask for your attention, but I will give up
 if you close it again.'''

 So, my code is more to an implementation of pattern '''Helper Classes'''
 than to a monkey patch.

 Let's think on '''django-tagging''', just for illustration. It is a good
 application, but let's consider that for a specific project I'd like to
 add a new field for model class '''Tag''': "icon" (an ImageField).

 Well, with actual state, I should to do one of the following:

  1. ask the author to add the field (of course would be insane to ask him
 to add a field just because I need for a specific project);
  2. fork it as my own '''my-project-django-tagging''' and modify it. Well,
 this would be the opposite of "'''DRY'''";

 But let's consider that the app's author made your "right" way, so I would
 use something like the setting AUTH_PROFILE_MODULE, so, let's name it
 "TAGGING_TAG_PROFILE" to add a field.

 Well, this could happen with any model class of any application (contribs,
 pluggable, public, privates, etc.), so to implement the "right" way as you
 said, would be to have a setting for each model class, so, IMO would be
 practically impossible or a totally mess.

 But, let's consider I would create a model class '''"TagProfile"''' and
 attach to that setting, so I would have a new model class with one field.
 So every code I write using tags I have to use a
 "my_tag.get_profile().icon" so we have the double of database requests for
 just one field.

 Another consequence is that I have two Admin modules: one for tagging.Tag
 and another one for my TagProfile (I could change
 '''admin.site._registry[Tag]''' but would be a classic monkey patch).

 And we must consider many times would be complicated to write
 aggregations, to use tag clouds, or even to use the applications features
 and going on...

 So, my ticket is about to implement a way to make single changes on third
 part (or contrib) applications without to make hard code.

 Actually, '''IMO''', User profiles never was a great solution, because it
 makes me to do the double of database requests and to have two places in
 Admin for the same reason, sometimes just to have a field like "website",
 so this is not really smart, actually users never understand why to change
 "website" is different to change "email". I use it because is a better way
 than inherit or make my own, but not really happy :)

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Re: [Django] #14969: To have a way to modify third part model classes

[Django]

#14969: To have a way to modify third part model classes
---+
  Reporter:  marinho   | Owner:  nobody
Status:  closed| Milestone:
 Component:  Database layer (models, ORM)  |   Version:  SVN   
Resolution:  wontfix   |  Keywords:
 Stage:  Unreviewed| Has_patch:  0 
Needs_docs:  0 |   Needs_tests:  0 
Needs_better_patch:  0 |  
---+
Changes (by russellm):

  * status:  new => closed
  * resolution:  => wontfix

Comment:

 Erm... No. Monkeypatching is bad, mmmkay?

 Comments gives you the *right* way to handle this problem -- you define an
 interface, and make the model itself pluggable. Not all Django's contrib
 apps follow this approach, but that doesn't mean we bake monkeypatching
 into the core -- we fix the contrib apps.

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Re: [Django] #14969: To have a way to modify third part model classes

[Django]

#14969: To have a way to modify third part model classes
---+
  Reporter:  marinho   | Owner:  nobody
Status:  new   | Milestone:
 Component:  Database layer (models, ORM)  |   Version:  SVN   
Resolution:|  Keywords:
 Stage:  Unreviewed| Has_patch:  0 
Needs_docs:  0 |   Needs_tests:  0 
Needs_better_patch:  0 |  
---+
Changes (by marinho):

  * needs_better_patch:  => 0
  * needs_tests:  => 0
  * needs_docs:  => 0

Comment:

 Fixing example code:

 {{{
 from django.db import models
 from django.contrib.auth.models import User

 from modify_models import ModifiedModel

 class ModifyingUser(ModifiedModel):
 class Meta:
 model = User
 exclude = ('first_name','last_name',)

 website = models.URLField(blank=True, verify_exists=False)

 def __unicode__(self):
 return '%s - %s'%(self.pk, self.name)
 }}}

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[Django] #14969: To have a way to modify third part model classes

[Django]

#14969: To have a way to modify third part model classes
--+-
 Reporter:  marinho   |   Owner:  nobody
   Status:  new   |   Milestone:
Component:  Database layer (models, ORM)  | Version:  SVN   
 Keywords:|   Stage:  Unreviewed
Has_patch:  0 |  
--+-
 Sometimes we need to modify a model class from a third part application or
 a Django's contrib, just for a specific project. The most common
 situations are related to the User, Group and Permission classes, like add
 new fields, or change __unicode__, etc.

 So I wrote this metaclass to allow us to modify a model class from another
 place of code without really change the original code.

 Basically you just inherit '''ModifiedModel''', set a '''Meta''' inner
 class with '''model = 'application.Model and set attributes with model
 fields, like below:

 """
 from django.db import models
 from django.contrib.auth.models import User

 from modify_models import ModifiedModel

 class ModifyingUser(ModifiedModel):
 class Meta:
 model = User
 exclude = ('first_name','last_name',)

 website = models.URLField(blank=True, verify_exists=False)

 def __unicode__(self):
 return '%s - %s'%(self.pk, self.name)
 """

 The code above adds a new field "website", excludes "first_name" and
 "last_name" and replaces the descriptor __unicode__ in the User model.

 In my projects and some of my clients sometimes we need this, so I thought
 it can be useful for other people and could be part of Django.

 I'm attaching a simple Python file to this ticket.

 If/when the ticket be approved I can work on documentations and tests and
 maybe improve the code to be part of the framework (i.e. re-think names).

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