While implementating Chandler's dashboard Bryan found that he needed better
control over the sorting of enumeration values.
Currently, enumeration values are strings and are sorted as such.
For example, if one defines an enumeration with the schema API as follows:
class TriageEnum(schema.Enumeration):
values = "now", "later", "done"
The values of this enumeration will be sorted as:
"done" < "later" < "now"
Enter a new type of enumeration, an enumeration of constants. Such constants
have a name and a value and are sorted on their value first. Multiple
constants in an enum may have the same value, their name is used next in
sorting.
By using a dict for the enumeration's values instead of a tuple, one can
define such a constant enumeration with the schema API:
class TriageEnum(schema.Enumeration):
values = {"now": 0, "later": 1, "done": -1}
Upon definition, the TriageEnum class gets assigned three attributes called
'now', 'later' and 'done' that contain such a constant:
TriageEnum.now -> TriageEnum.now
TriageEnum.now.value -> 0
TriageEnum.now.name -> 'now'
repr(TriageEnum.now) -> 'TriageEnum.now'
str(TriageEnum.name) -> 'now'
These constants are sorted by their values:
TriageEnum.done < TriageEnum.now < TriageEnum.later
Andi..
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