newforms: Implemented formfield() for database ForeignKey class and added unit tests

git-svn-id: http://code.djangoproject.com/svn/django/trunk@4247 bcc190cf-cafb-0310-a4f2-bffc1f526a37

django/db/models/fields/related.py

@@ -548,6 +548,9 @@ class ForeignKey(RelatedField, Field):
     def contribute_to_related_class(self, cls, related):
         setattr(cls, related.get_accessor_name(), ForeignRelatedObjectsDescriptor(related))
 
+    def formfield(self):
+        return forms.ChoiceField(choices=self.get_choices_default(), required=not self.blank, label=capfirst(self.verbose_name))
+
 class OneToOneField(RelatedField, IntegerField):
     def __init__(self, to, to_field=None, **kwargs):
         try:

tests/modeltests/model_forms/models.py

@@ -20,9 +20,16 @@ class Category(models.Model):
     def __str__(self):
         return self.name
 
+class Writer(models.Model):
+    name = models.CharField(maxlength=50)
+
+    def __str__(self):
+        return self.name
+
 class Article(models.Model):
     headline = models.CharField(maxlength=50)
     pub_date = models.DateTimeField()
+    writer = models.ForeignKey(Writer)
     categories = models.ManyToManyField(Category)
 
     def __str__(self):
@@ -101,12 +108,24 @@ Traceback (most recent call last):
 ...
 ValueError: The Category could not be created because the data didn't validate.
 
-ManyToManyFields are represented by a MultipleChoiceField.
+Create a couple of Writers.
+>>> w = Writer(name='Mike Royko')
+>>> w.save()
+>>> w = Writer(name='Bob Woodward')
+>>> w.save()
+
+ManyToManyFields are represented by a MultipleChoiceField, and ForeignKeys are
+represented by a ChoiceField.
 >>> ArticleForm = form_for_model(Article)
 >>> f = ArticleForm(auto_id=False)
 >>> print f
 <tr><th>Headline:</th><td><input type="text" name="headline" maxlength="50" /></td></tr>
 <tr><th>Pub date:</th><td><input type="text" name="pub_date" /></td></tr>
+<tr><th>Writer:</th><td><select name="writer">
+<option value="" selected="selected">---------</option>
+<option value="1">Mike Royko</option>
+<option value="2">Bob Woodward</option>
+</select></td></tr>
 <tr><th>Categories:</th><td><select multiple="multiple" name="categories">
 <option value="1">Entertainment</option>
 <option value="2">It&#39;s a test</option>