On 2012-08-22 04:35, Lester Caine wrote:
John LeSueur wrote:
Again, the case you've cited is probably not a case where generators
give much
advantage. But anytime the logic to produce some data becomes more
complicated
(Imagine that you needed to skip some of the lines in the .csv file
based on
some kind of filter), then being able to extricate the producer logic
from the
consumer logic is helpful.
But in my 'method of working' one simply changes the '$contact->' object
and loads the one that matches the data you are handling. Sage, paypal,
moneybox, nlpg and so on. I've a dozen or so data models currently.
>
That is one of the differences. With the Iterator pattern that is being
automated here, all the boilerplate of maintaining state between
iteration steps is contained within the iterator object, and is the same
for all uses of that object, so only needs to be written once (and, with
this extension, that writing is automated). Using the Observer pattern
like you do requires boilerplate to be written afresh for every distinct
_use_ of the iterator. That boilerplate isn't directly related to the
consumer's actual job but to the iteration process (limiting the range
of producers that consumer can be fed from).
but I still can't see why the work flow has to be
reorganised rather than simply following the natural flow that the job
requires.
The adjective "natural" would only apply if you always see iteration as
the producer pushing its productions out to the consumer ("here - go
work on this"), and never picture the situation as the consumer pulling
them from the producer ("give me something to work on"). Otherwise it's
just a different perspective.
The Observer pattern certainly does have its uses (otherwise it wouldn't
be a pattern): if the "things being produced" are interpreted as "events
being handled" ("hey, a new line of CSV has just come in!"), there may
be multiple consumers interested in being notified when those events occur.
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