Martin Aspeli wrote:
Brian Sutherland wrote:
[snip]
For some reason this raises a warning bell in my head. I keep on
thinking: this is zope, the session is a classic case for a utility, we
should be getting it in views by an interface.


FWIW, I had the same though.

I think there's a trade-off here: we can use patterns that SQLAlchemy and Pylons and others use directly (use a "global" that isn't actually global) or we can use patterns that are ubiquitous in Zope (look up utilities by interface).

To my mind, the latter is better because it makes us internally consistent, and because it promotes one of the formalisms that IMHO makes Zope 3 easier to work with.

The former integrates smoothly with SQLAlchemy. It also is closer to the SQLAlchemy documentation. It's also quite likely that someone writing a larger application that does use the interface lookup pattern will get bored and write something like:

def Session():
   return component.getUtility(ISession)

The Zope component architecture is not about seeing explicit calls into it everywhere. That's not the point of it. The point of it is about making applications more flexible by allowing people to plug in components. My approach allows you to do that.

Anyway, the balance can come out somewhere else. People are free to write their own integration approaches, it's just that mine is actually about trying to make exactly this pattern work in the first place. Then when I succeed people want it changed. :) Anyway, no surprise: I knew that some want other patterns, and I'll be curious to see the other approaches as well.

Regards,

Martijn

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