How do I create a Factory method in Python that generates different classes?

Question

Currently, I have the following:

class ConfirmStepAView(UpdateProcessView):
    form_class = ConfirmationForm

    def validate(self):
        if not self.process.A: 
            raise ValidationError

class ConfirmStepBView(UpdateProcessView):
    form_class = ConfirmationForm

    def validate(self):
        if not self.process.B: 
            raise ValidationError

# Usage: 
flow.View(ConfirmStepAView)
flow.View(ConfirmStepBView)

How can I write a factory method that generates these classes on the fly so I can do something like this?

flow.View(ConfirmStepViewFactory('A'))
flow.View(ConfirmStepViewFactory('B'))
flow.View(ConfirmStepViewFactory('Something'))
flow.View(ConfirmStepViewFactory('Else'))

Note: I have to use this format because I am working with a third part library.

cs95 · Accepted Answer · 2019-03-05 20:03:52Z

1

This is a common pattern. You can utilise closures in python to dynamically create and return your class.

def make_ConfirmStepView(attribute):
    class ConfirmStepView(UpdateProcessView):
        form_class = ConfirmationForm

        def validate(self):
            if not getattr(self.process, attribute): 
                raise ValidationError

    return ConfirmStepView

flow.View(make_ConfirmStepView('A'))
flow.View(make_ConfirmStepView('B'))
flow.View(make_ConfirmStepView('Something'))
flow.View(make_ConfirmStepView('Else'))

answered Mar 5, 2019 at 20:03

cs95

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