On Mar 16, 3:21 am, ALJ <astley.lejas...@gmail.com> wrote:
> This is a bit of a modeling question that I am struggling to get my
> head around. How would you model this scenario?
>
> I have to record expenses that are of 3 different types.
>
> 1. Fixed - The name of the expense and unit amount are fixed. For
> example, "inconvenience allowance" of £30 per day.
> 2. Classified - The name of the expense is fixed, but the actual unit
> amount isn't. For example "Hotel expenses". The actual unit amount
> will depend on the hotel they stay at. They'll need to enter that
> themselves.
> 3. Unclassified - The name of the expense and the amount is arbitrary.
> So they may have an expense we haven't thought of before but it needs
> to go in.
>
> Of course I'll need to create a summary that tots up the total
> expenses for the particular event.
whether you subclass a base model, or simply have a "type" field on
your expense object is going to depend on the details and nuance of
the rest of your business logic in your app. I would only say that
simple is better unless you have a reason or need for the complexity.
Given that the fields between them are identical, I would probably
just use a "type" choice field and have the interface adapt as needed.
-Preston
>
> Would the best way of doing this be:
>
> a) Have a base model and then build on that for the 3 different
> scenarios?
> b) Have three different tables and then do a union on them?
>
>
>
> Just for interest ... this is where I got so far, but am now stumped
>
> class CostType(models.Model):
> name = models.CharField("Name", max_length=30) 'e.g. commission,
> subsistence ...
>
> class CostItem(models.Model):
> name = models.CharField("Name", max_length=50) 'e.g. product x,
> inconvenience allowance, ...
> cost_type = models.ForeignKey(CostType, verbose_name="Type")
>
> class Rate(models.Model):
> cost_item = models.ForeignKey(CostItem, verbose_name="Item")
> valid_from = models.DateField("From")
> valid_till = models.DateField("Till")
> unit_amount = models.DecimalField("Price Per Unit", max_digits=5,
> decimal_places=2)
>
> 'Costs with a fixed description and unit amount
> class FixedCostList(models.Model):
> markettingevent= models.ForeignKey(Event)
> rate = models.ForeignKey(Rate)
> units = models.IntegerField()
>
> 'Costs with a fixed description but arbitrary amount
> class StructuredCostList(models.Model):
> markettingevent= models.ForeignKey(Event)
> cost_item = models.ForeignKey(CostItem, verbose_name="Item")
> unit_amount = models.DecimalField("Price Per Unit", max_digits=5,
> decimal_places=2)
> units = models.IntegerField()
>
> 'Costs with both a arbitrary description and amount
> class OtherCostList(models.Model):
> markettingevent= models.ForeignKey(Event)
> description = models.CharField("Name", max_length=30)
> unit_amount = models.DecimalField("Price Per Unit", max_digits=5,
> decimal_places=2)
> units = models.IntegerField()
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