From 649cdf907d5d23290caf3cc7e34426c39dfa4159 Mon Sep 17 00:00:00 2001 From: Jacob Kaplan-Moss Date: Wed, 19 Mar 2008 23:10:45 +0000 Subject: [PATCH] Fixed #4620: you can now easily add custom labels to ModelChoiceFields via subclassing. Thanks, PhiR. git-svn-id: http://code.djangoproject.com/svn/django/trunk@7326 bcc190cf-cafb-0310-a4f2-bffc1f526a37 --- django/newforms/models.py | 43 ++++++++++++++++---------- docs/newforms.txt | 18 ++++++++--- tests/modeltests/model_forms/models.py | 17 ++++++++++ 3 files changed, 57 insertions(+), 21 deletions(-) diff --git a/django/newforms/models.py b/django/newforms/models.py index f3809dc3707..0590839b252 100644 --- a/django/newforms/models.py +++ b/django/newforms/models.py @@ -277,19 +277,18 @@ class ModelForm(BaseModelForm): # Fields ##################################################################### -class QuerySetIterator(object): - def __init__(self, queryset, empty_label, cache_choices): - self.queryset = queryset - self.empty_label = empty_label - self.cache_choices = cache_choices +class ModelChoiceIterator(object): + def __init__(self, field): + self.field = field + self.queryset = field.queryset def __iter__(self): - if self.empty_label is not None: - yield (u"", self.empty_label) + if self.field.empty_label is not None: + yield (u"", self.field.empty_label) for obj in self.queryset: - yield (obj.pk, smart_unicode(obj)) + yield (obj.pk, self.field.label_from_instance(obj)) # Clear the QuerySet cache if required. - if not self.cache_choices: + if not self.field.cache_choices: self.queryset._result_cache = None class ModelChoiceField(ChoiceField): @@ -306,6 +305,7 @@ class ModelChoiceField(ChoiceField): help_text=None, *args, **kwargs): self.empty_label = empty_label self.cache_choices = cache_choices + # Call Field instead of ChoiceField __init__() because we don't need # ChoiceField.__init__(). Field.__init__(self, required, widget, label, initial, help_text, @@ -321,19 +321,30 @@ class ModelChoiceField(ChoiceField): queryset = property(_get_queryset, _set_queryset) + # this method will be used to create object labels by the QuerySetIterator. + # Override it to customize the label. + def label_from_instance(self, obj): + """ + This method is used to convert objects into strings; it's used to + generate the labels for the choices presented by this object. Subclasses + can override this method to customize the display of the choices. + """ + return smart_unicode(obj) + def _get_choices(self): # If self._choices is set, then somebody must have manually set # the property self.choices. In this case, just return self._choices. if hasattr(self, '_choices'): return self._choices + # Otherwise, execute the QuerySet in self.queryset to determine the - # choices dynamically. Return a fresh QuerySetIterator that has not - # been consumed. Note that we're instantiating a new QuerySetIterator - # *each* time _get_choices() is called (and, thus, each time - # self.choices is accessed) so that we can ensure the QuerySet has not - # been consumed. - return QuerySetIterator(self.queryset, self.empty_label, - self.cache_choices) + # choices dynamically. Return a fresh QuerySetIterator that has not been + # consumed. Note that we're instantiating a new QuerySetIterator *each* + # time _get_choices() is called (and, thus, each time self.choices is + # accessed) so that we can ensure the QuerySet has not been consumed. This + # construct might look complicated but it allows for lazy evaluation of + # the queryset. + return ModelChoiceIterator(self) def _set_choices(self, value): # This method is copied from ChoiceField._set_choices(). It's necessary diff --git a/docs/newforms.txt b/docs/newforms.txt index 26dde439efb..533ff75185b 100644 --- a/docs/newforms.txt +++ b/docs/newforms.txt @@ -1549,15 +1549,23 @@ additional required argument: ``ModelChoiceField`` ~~~~~~~~~~~~~~~~~~~~ -Allows the selection of a single model object, suitable for -representing a foreign key. +Allows the selection of a single model object, suitable for representing a +foreign key. The method receives an object as an argument and must return a +string to represent it. + +The labels for the choice field call the ``__unicode__`` method of the model to +generate string representations. To provide custom labels, subclass ``ModelChoiceField`` and override ``label_for_model``:: + + class MyModelChoiceField(ModelChoiceField): + def label_from_instance(self, obj): + return "My Object #%i" % obj.id ``ModelMultipleChoiceField`` ~~~~~~~~~~~~~~~~~~~~~~~~~~~~ -Allows the selection of one or more model objects, suitable for -representing a many-to-many relation. - +Allows the selection of one or more model objects, suitable for representing a +many-to-many relation. As with ``ModelChoiceField``, you can use +``label_from_instance`` to customize the object labels. Creating custom fields ---------------------- diff --git a/tests/modeltests/model_forms/models.py b/tests/modeltests/model_forms/models.py index a3c3ba21420..cda764de7ce 100644 --- a/tests/modeltests/model_forms/models.py +++ b/tests/modeltests/model_forms/models.py @@ -659,6 +659,19 @@ Traceback (most recent call last): ... ValidationError: [u'Select a valid choice. That choice is not one of the available choices.'] +# check that we can safely iterate choices repeatedly +>>> gen_one = list(f.choices) +>>> gen_two = f.choices +>>> gen_one[2] +(2L, u"It's a test") +>>> list(gen_two) +[(u'', u'---------'), (1L, u'Entertainment'), (2L, u"It's a test"), (3L, u'Third')] + +# check that we can override the label_from_instance method to print custom labels (#4620) +>>> f.queryset = Category.objects.all() +>>> f.label_from_instance = lambda obj: "category " + str(obj) +>>> list(f.choices) +[(u'', u'---------'), (1L, 'category Entertainment'), (2L, "category It's a test"), (3L, 'category Third'), (4L, 'category Fourth')] # ModelMultipleChoiceField #################################################### @@ -744,6 +757,10 @@ Traceback (most recent call last): ... ValidationError: [u'Select a valid choice. 4 is not one of the available choices.'] +>>> f.queryset = Category.objects.all() +>>> f.label_from_instance = lambda obj: "multicategory " + str(obj) +>>> list(f.choices) +[(1L, 'multicategory Entertainment'), (2L, "multicategory It's a test"), (3L, 'multicategory Third'), (4L, 'multicategory Fourth')] # PhoneNumberField ############################################################