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PODjango custom field with multiple inheritance
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copied!<p>I have two custom Django fields, a <code>JSONField</code> and a <code>CompressedField</code>, both of which work well. I would like to also have a <code>CompressedJSONField</code>, and I was rather hoping I could do this:</p> <pre><code>class CompressedJSONField(JSONField, CompressedField): pass </code></pre> <p>but on import I get:</p> <pre><code>RuntimeError: maximum recursion depth exceeded while calling a Python object </code></pre> <p>I can find information about using models with multiple inheritance in Django, but nothing about doing the same with fields. Should this be possible? Or should I just give up at this stage?</p> <p><strong>edit:</strong></p> <p>Just to be clear, I don't <em>think</em> this has anything to do with the specifics of my code, as the following code has exactly the same problem:</p> <pre><code>class CustomField(models.TextField, models.CharField): pass </code></pre> <p><strong>edit 2:</strong></p> <p>I'm using Python 2.6.6 and Django 1.3 at present. Here is the full code of my stripped-right-down test example:</p> <h2><code>customfields.py</code></h2> <pre><code>from django.db import models class CompressedField(models.TextField): """ Standard TextField with automatic compression/decompression. """ __metaclass__ = models.SubfieldBase description = 'Field which compresses stored data.' def to_python(self, value): return value def get_db_prep_value(self, value, **kwargs): return super(CompressedField, self)\ .get_db_prep_value(value, prepared=True) class JSONField(models.TextField): """ JSONField with automatic serialization/deserialization. """ __metaclass__ = models.SubfieldBase description = 'Field which stores a JSON object' def to_python(self, value): return value def get_db_prep_save(self, value, **kwargs): return super(JSONField, self).get_db_prep_save(value, **kwargs) class CompressedJSONField(JSONField, CompressedField): pass </code></pre> <h2><code>models.py</code></h2> <pre><code>from django.db import models from customfields import CompressedField, JSONField, CompressedJSONField class TestModel(models.Model): name = models.CharField(max_length=150) compressed_field = CompressedField() json_field = JSONField() compressed_json_field = CompressedJSONField() def __unicode__(self): return self.name </code></pre> <p>as soon as I add the <code>compressed_json_field = CompressedJSONField()</code> line I get errors when initializing Django.</p>

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