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GitHub User: leisti
@psingh: starting at 6:30, the cast explains that if you add "filter_resource_access" to a controller declaration, the gem will automatically take care of that for you.
Because you should avoid premature optimization and premature refactoring. Maybe you'll need it, maybe you won't. In the former case, you can do it when you need it. In the latter case, you'll have wasted effort by doing premature work.