I'd like to store extra attributes in the model fields so I can
control the subsequent field-specific behavior from there.
Let's say I have a model that stores metrics I then need to chart.
In the view, I prefer not to have some logic that says:
metrics = Metric.object.all()
create_chart([metric.productivity for metric in metrics], "bar_chart")
create_chart([metric.defects for metric in metrics], "pie_chart")
I'd rather have something like:
for metric_type in Metric.fields:
create_chart([metric."metric_type" for metric in metrics],
metric."metric_type".chart_type)
The big advantage here is that I can add a new metrics element from
the model without changing the view (Open-Close principle...)
So it would be great if I could do something like:
class Metric(models.Model):
productivity = PositiveIntegerField(
verbose_name = "the number of hot dogs we have produced during
that period",
chart_type = "bar_chart"
)
...
However the model rejects fields it does not recognize.
I tried creating my own doctored model to wrap the built-in models:
class _PositiveIntegerField(models.fields.CharField):
def __init__(self, *args, **kwargs):
if "extra_attrs" in kwargs:
self.extra_attrs = kwargs["extra_attrs"]
del kwargs["extra_attrs"]
models.fields.PositiveIntegerField.__init__(self, *args,
**kwargs)
This way I can do:
class Metric(models.Model):
productivity = _PositiveIntegerField(
verbose_name = "the number of hot dogs we have produced during
that period",
extra_attrs = {'chart_type' : "bar_chart"}
)
...
There are two problems here:
1. I'd need to wrap every field type
2. In the ModelForm I create from this model the type still registers
as the built-in type:
class MetricForm(models.ModelForm):
class Meta:
model = Metric
>>> mf = MetricForm()
>>> mf.fields['productivity']
<django.forms.fields.PositiveIntegerField object at 0x12312312>
Any suggestion as to how to design this right?
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