[Zope3-dev] service names

[Shane Hathaway]

Jim Fulton wrote:
> Steve Alexander wrote:
> 
>> sean.bowman@acm.org wrote:
>>
>>> hello,
>>>
>>> In all the code I've seen in Z3, the second argument to getService is a
>>> string literal.  This smells bad to me -- it seems to violate Once And
>>> Only Once.  Would it be a good idea to use a constant instead of a 
>>> string
>>> literal?  For example::
>>>
>>>   getService(context, defaultHubIdsName)
>>
>>
>>
>> Why not just HubIds ?
>>
>>   HubIds = 'HubIds'
>>   getService(context, HubIds)
> 
> 
> Why not just 'HubIds'?
> 
> I really fail to see the benefit of a variable or a marker interface here.

I've been pondering this for a few days.  I like to use global variables 
as constants to shield myself from certain typos.  In the example below, 
'Id' is sometimes misspelled 'ID':

queryService(context, HubIds) -> hub IDs service
queryService(context, HubIDs) -> NameError
queryService(context, 'HubIds') -> hub IDs service
queryService(context, 'HubIDs') -> None

In the last case, the error might go undetected.  So there is at least 
one benefit to using a variable.  It's not terribly important, but I 
thought it was worth mentioning. :-)

Shane