{"id":439,"date":"2013-03-09T16:30:16","date_gmt":"2013-03-09T20:30:16","guid":{"rendered":"http:\/\/dashdrum.com\/blog\/?p=439"},"modified":"2013-03-09T16:30:16","modified_gmt":"2013-03-09T20:30:16","slug":"custom-errorlist-in-a-form","status":"publish","type":"post","link":"https:\/\/dashdrum.com\/blog\/2013\/03\/custom-errorlist-in-a-form\/","title":{"rendered":"Custom ErrorList in a Form"},"content":{"rendered":"

I was playing around with a custom ErrorList the other day. The idea is to be able modify the way errors display in a template. The Django documentation gives an example of this technique<\/a>.<\/p>\n

(One thing I noticed while overriding methods in ErrorList, when I only defined one of the existing display methods, such as as_ul<\/code>, the code was ignored. Only when I also included my own __unicode__<\/code> method pointing to my new code did it work correctly. I’m using Django 1.3 right now, so you may find things better in a future version.)<\/p>\n

My challenge was to use my custom ErrorList with a form in a class-based views environment. There are several ways to accomplish this.<\/p>\n

Handle It in the View<\/h2>\n

In the view, one can override the get_form_kwargs<\/code> method to add the error_class<\/code> attribute to the kwargs<\/code> dictionary.<\/p>\n

def get_form_kwargs(self):\n\n    kwargs = super(MyViewName,self).get_form_kwargs()\n\n    kwargs.update({'error_class': MyCustomErrorList})\n\n    return kwargs\n<\/code><\/pre>\n
Since I’m a big mixin fan, I developed this little gem that performs this task:<\/p>\n
class CustomErrorClassViewMixin(object):\n\n    ''' Will set the error_class attribute\n        on the form with the provided value \n        found in the error_class variable  '''\n\n    error_class = None\n\n    def get_form_kwargs(self):\n        # Make sure that the error_class attribute is set on the\n        # view, or raise a configuration error.\n        if self.error_class is None:\n            raise ImproperlyConfigured(\"'CustomErrorClassViewMixin' requires \"\n                \"'error_class' attribute to be set.\")\n\n        kwargs = super(CustomErrorClassViewMixin,self).get_form_kwargs()\n\n        kwargs.update({'error_class': self.error_class})\n\n        return kwargs\n<\/code><\/pre>\n
Include this mixin in your view class definition (class MyView(CustomErrorClassViewMixin, CreateView)<\/code>) and set a value for the error_class<\/code> variable, and it will handle the rest.<\/p>\n
Form Level Fun<\/h2>\n
In some situations, it may be desired to use the custom ErrorList on every use of the form.  To do this, a little work in the form’s __init__<\/code> method is required.<\/p>\n
def __init__(self, *args, **kwargs):\n    ## Set the error_class attribute\n    kwargs['error_class'] = MyCustomErrorList\n\n    ## Call the parent method\n    super(MyForm, self).__init__(*args, **kwargs)\n<\/code><\/pre>\n
Here’s a mixin for this scenario (I love the mixins!):<\/p>\n
class CustomErrorClassFormMixin(object):\n''' Allows the declaration of a custom error_class for a form\n\n    Requires the error_class attribute to be provided \n'''\n\n    error_class = None ## Default to none\n\n    def __init__(self, *args, **kwargs):\n        # Make sure that the error_class attribute is set on the\n        # form, or raise a configuration error.\n        if self.error_class is None:\n            raise ImproperlyConfigured(\"'CustomErrorClassFormMixin' requires \"\n                \"'error_class' attribute to be set.\")\n\n        ## Set the error_class attribute\n        kwargs['error_class'] = self.error_class\n\n        ## Call the parent method\n        super(CustomErrorClassFormMixin, self).__init__(*args, **kwargs)\n<\/code><\/pre>\n
A couple of notes for this one:<\/p>\n