Hi aditya, I wasn't aware of the editable parameter (which means I've learnt something) but I still don't think it will help me.
The user will create an 'invoice' for want of a better word, that will be made up of lots of different entries. Some of these are fixed (description and unit price) and therefore selected from a list of options, some are classified (description) but can enter a unit price, and some are unclassified so they will need to enter free text description and unit cost. Eg Type, Description, unit price, units Fixed, Commission on Product XXX, £20, [12] Fixed, Commission on Product YYY, £18, [4] Fixed, Inconvenience allowance, £30, [2] Classified, Parking fees, [£10], [1] Classified, Hotel, [£100], [2] Unclassified, [Emergency Courier we didn't think we'd need], [£50], [1] [] = user entered, > How will the model be used? It looks to me like what you're after is > the 'editable' parameter, as in something like: > class Unclassified(models.Model): > name = models.CharField(max_length=50) > cost = models.DecimalField(max_digits=5,decimal_places=2) > > class Classified(Unclassified): > name = > models.CharField(default="Hotels",editable=False,max_length=50) > > class Fixed(Unclassified): > name = models.Charfield(editable=False,max_length=50) > cost = > models.DecimalField(max_digits=5,decimal_places=2,editable=False) > > On Mar 16, 9:36 am, ALJ <[email protected]> wrote: > > > Hi Preston, > > > Sorry, I don't get it. > > > The certainly do have the same fields, but sometimes the fields are > > derived from a linked table, or are a foreign key or sometimes text. > > So I don't understand how having the interface adapt to what the > > current type is would work. > > > ALJ > > > On Mar 16, 3:04 pm, Preston Holmes <[email protected]> wrote: > > > > On Mar 16, 3:21 am, ALJ <[email protected]> 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() -- You received this message because you are subscribed to the Google Groups "Django users" group. 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