Steel Sky

Not that it's a particularly common use case, I suppose, but still, it's worth noting. I was trying to use a Scala paradigm (computed values) in Python, so I'm not surprised. The code that failed:

class Category(models.Model):
    title = models.CharField(max_length = 50, unique = True)
    
    uncategorizedTitle = "Uncategorised"
    
    @classmethod
    def getUncategorised(cls):
        uncategorizedList = Category.objects.all().filter(title=cls.uncategorizedTitle)
        if uncategorizedList:
            return uncategorizedList[0]
        else:
            uncategorized = Category(title=Category.uncategorizedTitle)
            uncategorized.save()
            return uncategorized
        
    uncategorised = property(fset=getUncategorised)
        
class BlogEntry(models.Model):
    
    category = models.ForeignKey(Category, blank=True, null = True)
        
    def save(self):        
        if not self.category:                
            self.category = Category.uncategorised
                
        super(BlogEntry, self).save()

Removing the property and just calling the method directly works as expected. Admittedly, doing it as a property was entirely unnecessary syntactic sugar, no doubt stemming from the semantic connotations that I associate with the Enum.SpecificSubType syntax.

For an explanation of what I mean by a computed value, here's a pseudo-Scala transliteration of the Category code (without the pretty colours, unfortunately):

class Category extends models.Model {
    var title = new models.CharField(50, True)
}

object Category {
    val uncategorisedTitle = "Uncategorised"
   
    let uncategorised = {
        Category.objects.all().filter(title == uncategorisedTitle) match {
            Nil => {
                uncategorised = new Category(Map("title" -> "uncategorisedTitle"))
                uncategorised.save()
                uncategorised
            }
            first :: _ => {
                first
            }
        }
    }
}