actions in django

Question

How can i enable or disable actions according to the value of a field.For example In my model I have a status field which can have either of the value 'activate','pending','expired'.I am making a action which set the status equals to 'activate'.Know I want the action to be enable only if status is 'pending'.

Answer 1

This is some combination of the Strategy and State design patterns.

You'll be defining method functions for the action, and you'll want that method function to be sensitive to the state of your model instance.

Here's what we do.

class SpecialProcessing( object ):
    def __init__( self, aModelObject ):
        self.modelObject= aModelObject
    def someMethod( self ):
        pass

class SpecialProcessingActivate( SpecialProcessing ):
    def someMethod( self ):
        # do work if possible or raise exception of not possible

class SpecialProcessingPending( SpecialProcessing ):
    def someMethod( self ):
        # do work if possible or raise exception of not possible

class SpecialProcessingExpired( SpecialProcessing ):
    def someMethod( self ):
        # do work if possible or raise exception of not possible

class MyObject( models.Model ):
    status = models.CharField( max_length = 1 )
    def setState( self ):
        if self.status == "a":
            self.state = SpecialProcessingActivate(self)
        elif self.status == "p":
            self.state = SpecialProcessingPending(self)
        elif self.status == "x":
            self.state = SpecialProcessingExpired(self)
        else:
            raise Exception( "Ouch!" )
    def doSomething( self ):
        self.setState()
        self.state.someMethod()

This way, we can add new states (and state transition rules) freely without disturbing the model class too much.

Answer 2

Admin action methods provide you a queryset. Just slap an exclude or filter for pending

Answer 3

i think using queryset is good approach