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by dasil003
5757 days ago
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I don't get your point. Just because you may have to do some things in a before_filter or whatever doesn't mean you need to do all things there. As far as accessing stuff out of memcached is concerned, there's no reason that can't also be deferred to the view. Claiming that lazy loaded queries is only a benefit for "trival cases" is a strawman. It's a hugely powerful functionality for ActiveRecord that you can utilize in many ways, and would be very hard to implement without low level support. Cached attributes can often easily be made available via concise single model methods that operate transparently without the controller OR the view needing to know they are cache-backed. Plus, even if you are loading stuff out of memcached in the controller, it's going to be fast, because that's the whole point of memcached. ActiveRecord meanwhile, normally takes a huge percentage of rendering time. Being able to defer those queries while still allowing the controller to declare them is actually a huge combination of performance flexibility and separation of concerns. Previously, if you wanted to defer them "cleanly", you'd have to create model methods, but even there you would have to pass params through somehow or generally do something uglier than what you have to do now. |
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1.The performance goal is to return http & html headers as quickly as possible.
2. Business logic belongs in the models, as triggered by method invocations from the controller.
3. A good deal of time is spent on business logic and request handling (authentication / set-up / before_filter stuff.) Often, this requires network I/O to backend systems (or databases.) While some data retrieval is necessary only to render the view (and can thus be deferred gracefully,) other times your application logic depends the completion of these lengthy requests in order to complete the desired state modification.
4. Since we want to return the headers as quickly as possible, we can either a) figure out how to send the headers before the controller or b) figure out how to delay the processing until after the controller.
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I think that that a) is better than b).
I like views that exclusively take data and format it for output. I like having the core business logic in the models, and I like having the system guards and request setup concentrated in the controllers. This way, I can have an exhaustive understanding of the tasks performed by an action without having to read through all of the views and their partials.
If we hide some of the processing within model actions and call those model actions from the view, then I no longer can assume that all major processing / I/O has happened by simply reading the controller and the model methods it invokes. Instead, I also have to read all of the views.
This violates the expectations I have about processing times and MVC.
If instead, we could detect the requested format and return immediately with the headers, then we could perform the overwhelming majority of the processing while the browser is busy downloading static assets.