[Chandler-dev] Defining a sort order for schema.Enumerations

[Bryan Stearns]

Hi pje,

I need to sort ContentItems by triageStatus, where 'triageStatus' is a 
TriageEnum attribute:

class TriageEnum(schema.Enumeration):
    schema.kindInfo(displayName=_(u"Triage Status Enum"))
    values = "now", "later", "done"

class ContentItem(schema.Item):
    triageStatus = schema.One(TriageEnum, indexed=True,
                              displayName=_(u"Triage Status"),
                              initialValue="now")

Currently, we're sorting by the raw attribute value -- essentially, 
key=lambda x: x.triageStatus -- but this sorts alphabetically: "done", 
"later", "now"; it's really supposed to sort in the order the values are 
given.

* My initial thought was to add something like this to the TriageEnum 
declaration:

class TriageEnum(schema.Enumeration):
    ...
    ordering = dict((v, i) for (i, v) in enumerate(values))

because then I could do something like key=lambda x: 
ContentItem.triageStatus.type.ordering[x.triageStatus]

However, this would only work for TriageStatus, and this seems like 
something useful for all schema.Enumeration-based attributes.

* so I was thinking about ways to generalize this to any 
schema.Enumeration-based type... This may make you cringe, but adding 
this line to the end of EnumerationClass.__init__ did the trick:

class EnumerationClass(Activator):
    def __init__(cls,name,bases,cdict):
        [...]
        cls.ordering = dict((v, i) for (i, v) in enumerate(cls.values))

Or can you suggest a better way to accomplish this? (I'd also considered 
just figuring out the values index within the lambda, but this seemed 
inefficient, especially since there's no .index on tuples :-( ...)

Thanks,
...Bryan