Howto: Django Forms with Dynamic Fields

Posted by Alexander Todorov on Sat 03 May 2014

Last week at HackFMI 3.0 one team had to display a form which presented multiple choice selection for filtering, where the filter keys are read from the database. They've solved the problem by simply building up the HTML required inside the view. I was wondering if this can be done with forms.

>>> from django import forms
>>>
>>> class MyForm(forms.Form):
...     pass
...
>>> print(MyForm())

>>> MyForm.__dict__['base_fields']['name'] = forms.CharField()
>>> MyForm.__dict__['base_fields']['age'] = forms.IntegerField()
>>> print(MyForm())
<tr><th><label for="id_name">Name:</label></th><td><input id="id_name" name="name" type="text" /></td></tr>
<tr><th><label for="id_age">Age:</label></th><td><input id="id_age" name="age" type="number" /></td></tr>
>>>
>>>
>>> POST = {'name' : 'Alex', 'age' : 0}
>>> f = MyForm(POST)
>>> print(f)
<tr><th><label for="id_name">Name:</label></th><td><input id="id_name" name="name" type="text" value="Alex" /></td></tr>
<tr><th><label for="id_age">Age:</label></th><td><input id="id_age" name="age" type="number" value="0" /></td></tr>
>>> f.is_valid()
True
>>> f.is_bound
True
>>> f.errors
{}
>>> f.cleaned_data
{'age': 0, 'name': u'Alex'}

So if we were to query all names from the database then we could build up the class by adding a BooleanField using the object primary key as the name.

>>> MyForm.__dict__['base_fields']['123'] = forms.BooleanField()
>>> print(MyForm())
<tr><th><label for="id_123">123:</label></th><td><input id="id_123" name="123" type="checkbox" /></td></tr>
>>> f = MyForm({'123' : True})
>>> f.is_valid()
True
>>> f.cleaned_data
{'123': True}

tags: Django

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