Ruby on Rails

On 24 April 2014 15:53, ngollan@googlemail.com <ngollan@gmail.com> wrote:
> FWIW, no, it is not possible to do that without a LOT of sanitation of
> Rails/ActiveRecord code.

For those of us with less knowledge of how the internals of rails
works could you provide a simple example of what you are attempting to
achieve with dynamic class name in a association?

Thanks

Colin

>
> The problem is that the <extremely competent and forward-looking> developers
> decided to do all the heavy lifting in reflections instead of the
> associations. Why is that a problem? Because reflections *have no
> information AT ALL* about the specific association they are being used for.
>
> Example: you have a model "Dog" that has_many :bones.
>
> Now: dog = Dog.first; dog.bones #=> Array
>
> Ignore the "Array" part, that's due to idiocy of the framework (basically
> AssociationProxy tries to be a BasicObject and fails *hard*). The framework
> at that point does the actual lookup through an "association proxy" which
> has a lot of information: the specific dog, ultimately all the bones, and
> additionally the reflection which has all information about the "has_many"
> call. Rails then goes on to basically throw away all the nice information
> from the association proxy, turns to the reflection, and ends up with two
> methods: Reflection#class_name and the derived #class_name, both of which
> boil down to either a value derived from the association name itself, or the
> :class_name option.
>
> Now you might think, alright, I'll just do some minimal hacking and fix
> stuff so Reflection#class_name looks up the "left side" of the association
> call. That won't work, because (1) the reflection is really just a dumb
> memoisation of the has_many call, and (2) it's pretty much a singleton, so
> if you change it, you'll break your entire runtime.
>
> You might also think that you could fix up the AssociationProxy. That's a
> better thought since it konws about the owner model and can just call
> aribtrary methods in there, but then you spend 4 hours on it, just to
> realise that later on the framework decides to use Reflection#chain and
> effectively bypasses all your fancy work when trying to build the scope for
> the final query.
>
> All in all, it's another case of Rails/AR being a humongous pile of
> <organically-grown code> that is pretty much unadaptable to your fancy
> concepts unless you want to sit down and rewrite large parts of it.
>
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