mirror of https://github.com/django/django.git
285 lines
10 KiB
Python
285 lines
10 KiB
Python
"""
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34. Generating HTML forms from models
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Django provides shortcuts for creating Form objects from a model class and a
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model instance.
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The function django.newforms.form_for_model() takes a model class and returns
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a Form that is tied to the model. This Form works just like any other Form,
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with one additional method: save(). The save() method creates an instance
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of the model and returns that newly created instance. It saves the instance to
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the database if save(commit=True), which is default. If you pass
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commit=False, then you'll get the object without committing the changes to the
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database.
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The function django.newforms.form_for_instance() takes a model instance and
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returns a Form that is tied to the instance. This form works just like any
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other Form, with one additional method: save(). The save()
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method updates the model instance. It also takes a commit=True parameter.
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The function django.newforms.save_instance() takes a bound form instance and a
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model instance and saves the form's clean_data into the instance. It also takes
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a commit=True parameter.
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"""
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from django.db import models
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class Category(models.Model):
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name = models.CharField(maxlength=20)
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url = models.CharField('The URL', maxlength=40)
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def __str__(self):
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return self.name
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class Writer(models.Model):
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name = models.CharField(maxlength=50, help_text='Use both first and last names.')
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def __str__(self):
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return self.name
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class Article(models.Model):
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headline = models.CharField(maxlength=50)
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pub_date = models.DateField()
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writer = models.ForeignKey(Writer)
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article = models.TextField()
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categories = models.ManyToManyField(Category, blank=True)
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def __str__(self):
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return self.headline
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__test__ = {'API_TESTS': """
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>>> from django.newforms import form_for_model, form_for_instance, save_instance, BaseForm, Form, CharField
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>>> import datetime
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>>> Category.objects.all()
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[]
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>>> CategoryForm = form_for_model(Category)
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>>> f = CategoryForm()
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>>> print f
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<tr><th><label for="id_name">Name:</label></th><td><input id="id_name" type="text" name="name" maxlength="20" /></td></tr>
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<tr><th><label for="id_url">The URL:</label></th><td><input id="id_url" type="text" name="url" maxlength="40" /></td></tr>
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>>> print f.as_ul()
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<li><label for="id_name">Name:</label> <input id="id_name" type="text" name="name" maxlength="20" /></li>
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<li><label for="id_url">The URL:</label> <input id="id_url" type="text" name="url" maxlength="40" /></li>
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>>> print f['name']
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<input id="id_name" type="text" name="name" maxlength="20" />
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>>> f = CategoryForm(auto_id=False)
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>>> print f.as_ul()
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<li>Name: <input type="text" name="name" maxlength="20" /></li>
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<li>The URL: <input type="text" name="url" maxlength="40" /></li>
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>>> f = CategoryForm({'name': 'Entertainment', 'url': 'entertainment'})
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>>> f.is_valid()
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True
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>>> f.clean_data
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{'url': u'entertainment', 'name': u'Entertainment'}
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>>> obj = f.save()
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>>> obj
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<Category: Entertainment>
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>>> Category.objects.all()
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[<Category: Entertainment>]
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>>> f = CategoryForm({'name': "It's a test", 'url': 'test'})
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>>> f.is_valid()
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True
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>>> f.clean_data
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{'url': u'test', 'name': u"It's a test"}
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>>> obj = f.save()
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>>> obj
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<Category: It's a test>
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>>> Category.objects.all()
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[<Category: Entertainment>, <Category: It's a test>]
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If you call save() with commit=False, then it will return an object that
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hasn't yet been saved to the database. In this case, it's up to you to call
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save() on the resulting model instance.
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>>> f = CategoryForm({'name': 'Third test', 'url': 'third'})
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>>> f.is_valid()
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True
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>>> f.clean_data
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{'url': u'third', 'name': u'Third test'}
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>>> obj = f.save(commit=False)
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>>> obj
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<Category: Third test>
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>>> Category.objects.all()
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[<Category: Entertainment>, <Category: It's a test>]
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>>> obj.save()
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>>> Category.objects.all()
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[<Category: Entertainment>, <Category: It's a test>, <Category: Third test>]
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If you call save() with invalid data, you'll get a ValueError.
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>>> f = CategoryForm({'name': '', 'url': 'foo'})
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>>> f.errors
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{'name': [u'This field is required.']}
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>>> f.clean_data
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Traceback (most recent call last):
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...
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AttributeError: 'CategoryForm' object has no attribute 'clean_data'
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>>> f.save()
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Traceback (most recent call last):
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...
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ValueError: The Category could not be created because the data didn't validate.
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>>> f = CategoryForm({'name': '', 'url': 'foo'})
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>>> f.save()
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Traceback (most recent call last):
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...
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ValueError: The Category could not be created because the data didn't validate.
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Create a couple of Writers.
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>>> w = Writer(name='Mike Royko')
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>>> w.save()
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>>> w = Writer(name='Bob Woodward')
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>>> w.save()
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ManyToManyFields are represented by a MultipleChoiceField, and ForeignKeys are
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represented by a ChoiceField.
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>>> ArticleForm = form_for_model(Article)
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>>> f = ArticleForm(auto_id=False)
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>>> print f
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<tr><th>Headline:</th><td><input type="text" name="headline" maxlength="50" /></td></tr>
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<tr><th>Pub date:</th><td><input type="text" name="pub_date" /></td></tr>
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<tr><th>Writer:</th><td><select name="writer">
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<option value="" selected="selected">---------</option>
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<option value="1">Mike Royko</option>
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<option value="2">Bob Woodward</option>
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</select></td></tr>
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<tr><th>Article:</th><td><textarea name="article"></textarea></td></tr>
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<tr><th>Categories:</th><td><select multiple="multiple" name="categories">
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<option value="1">Entertainment</option>
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<option value="2">It's a test</option>
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<option value="3">Third test</option>
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</select><br /> Hold down "Control", or "Command" on a Mac, to select more than one.</td></tr>
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You can pass a custom Form class to form_for_model. Make sure it's a
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subclass of BaseForm, not Form.
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>>> class CustomForm(BaseForm):
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... def say_hello(self):
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... print 'hello'
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>>> CategoryForm = form_for_model(Category, form=CustomForm)
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>>> f = CategoryForm()
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>>> f.say_hello()
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hello
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Use form_for_instance to create a Form from a model instance. The difference
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between this Form and one created via form_for_model is that the object's
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current values are inserted as 'initial' data in each Field.
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>>> w = Writer.objects.get(name='Mike Royko')
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>>> RoykoForm = form_for_instance(w)
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>>> f = RoykoForm(auto_id=False)
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>>> print f
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<tr><th>Name:</th><td><input type="text" name="name" value="Mike Royko" maxlength="50" /><br />Use both first and last names.</td></tr>
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>>> art = Article(headline='Test article', pub_date=datetime.date(1988, 1, 4), writer=w, article='Hello.')
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>>> art.save()
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>>> art.id
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1
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>>> TestArticleForm = form_for_instance(art)
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>>> f = TestArticleForm(auto_id=False)
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>>> print f.as_ul()
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<li>Headline: <input type="text" name="headline" value="Test article" maxlength="50" /></li>
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<li>Pub date: <input type="text" name="pub_date" value="1988-01-04" /></li>
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<li>Writer: <select name="writer">
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<option value="">---------</option>
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<option value="1" selected="selected">Mike Royko</option>
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<option value="2">Bob Woodward</option>
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</select></li>
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<li>Article: <textarea name="article">Hello.</textarea></li>
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<li>Categories: <select multiple="multiple" name="categories">
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<option value="1">Entertainment</option>
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<option value="2">It's a test</option>
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<option value="3">Third test</option>
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</select> Hold down "Control", or "Command" on a Mac, to select more than one.</li>
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>>> f = TestArticleForm({'headline': u'New headline', 'pub_date': u'1988-01-04', 'writer': u'1', 'article': 'Hello.'})
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>>> f.is_valid()
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True
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>>> new_art = f.save()
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>>> new_art.id
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1
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>>> new_art = Article.objects.get(id=1)
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>>> new_art.headline
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'New headline'
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Add some categories and test the many-to-many form output.
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>>> new_art.categories.all()
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[]
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>>> new_art.categories.add(Category.objects.get(name='Entertainment'))
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>>> new_art.categories.all()
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[<Category: Entertainment>]
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>>> TestArticleForm = form_for_instance(new_art)
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>>> f = TestArticleForm(auto_id=False)
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>>> print f.as_ul()
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<li>Headline: <input type="text" name="headline" value="New headline" maxlength="50" /></li>
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<li>Pub date: <input type="text" name="pub_date" value="1988-01-04" /></li>
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<li>Writer: <select name="writer">
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<option value="">---------</option>
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<option value="1" selected="selected">Mike Royko</option>
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<option value="2">Bob Woodward</option>
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</select></li>
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<li>Article: <textarea name="article">Hello.</textarea></li>
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<li>Categories: <select multiple="multiple" name="categories">
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<option value="1" selected="selected">Entertainment</option>
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<option value="2">It's a test</option>
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<option value="3">Third test</option>
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</select> Hold down "Control", or "Command" on a Mac, to select more than one.</li>
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>>> f = TestArticleForm({'headline': u'New headline', 'pub_date': u'1988-01-04',
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... 'writer': u'1', 'article': u'Hello.', 'categories': [u'1', u'2']})
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>>> new_art = f.save()
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>>> new_art.id
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1
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>>> new_art = Article.objects.get(id=1)
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>>> new_art.categories.all()
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[<Category: Entertainment>, <Category: It's a test>]
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Now, submit form data with no categories. This deletes the existing categories.
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>>> f = TestArticleForm({'headline': u'New headline', 'pub_date': u'1988-01-04',
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... 'writer': u'1', 'article': u'Hello.'})
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>>> new_art = f.save()
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>>> new_art.id
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1
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>>> new_art = Article.objects.get(id=1)
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>>> new_art.categories.all()
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[]
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Create a new article, with categories, via the form.
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>>> ArticleForm = form_for_model(Article)
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>>> f = ArticleForm({'headline': u'The walrus was Paul', 'pub_date': u'1967-11-01',
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... 'writer': u'1', 'article': u'Test.', 'categories': [u'1', u'2']})
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>>> new_art = f.save()
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>>> new_art.id
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2
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>>> new_art = Article.objects.get(id=2)
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>>> new_art.categories.all()
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[<Category: Entertainment>, <Category: It's a test>]
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Create a new article, with no categories, via the form.
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>>> ArticleForm = form_for_model(Article)
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>>> f = ArticleForm({'headline': u'The walrus was Paul', 'pub_date': u'1967-11-01',
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... 'writer': u'1', 'article': u'Test.'})
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>>> new_art = f.save()
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>>> new_art.id
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3
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>>> new_art = Article.objects.get(id=3)
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>>> new_art.categories.all()
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[]
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Here, we define a custom Form. Because it happens to have the same fields as
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the Category model, we can use save_instance() to apply its changes to an
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existing Category instance.
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>>> class ShortCategory(Form):
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... name = CharField(max_length=5)
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... url = CharField(max_length=3)
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>>> cat = Category.objects.get(name='Third test')
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>>> cat
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<Category: Third test>
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>>> cat.id
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3
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>>> sc = ShortCategory({'name': 'Third', 'url': '3rd'})
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>>> save_instance(sc, cat)
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<Category: Third>
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>>> Category.objects.get(id=3)
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<Category: Third>
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"""}
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