Discussion of a stable reflection API

[jhollinger]

As a follow up to the discussion in #294, things like auto-preloading of ActiveRecord associations could be done through Blueprinter extensions if there was some kind of reflection API available (think ActiveRecord's reflections or columns_hash).

I've been experimenting with such an extension and have a good handle on what kind of info it needs from Blueprinter (essentially "give me all the associations for view X recursively"). But I don't want to design something overly-specific, so I'm hoping to gather some feedback. As a point of reference, here's some POC work:

This is non-invasive to Blueprinter, aside from requesting all the associations from the view. The duplication of the Blueprinter class and view isn't ideal.

q = Widget.
  where(...).
  order(...).
  preload_blueprint(WidgetBlueprint, :extended)

render json: WidgetBlueprint.render(q, view: :extended)

Here's a centralized version without the duplication. === is used to match objects passed to render, and the result of the block is passed to the render pipeline. Vaguely like a centralized transformer.

# config/initializers/blueprinter.rb

Blueprinter.configure do |config|
  config.generator = Oj
  config.on_render ActiveRecord::Relation do |scope, blueprint, view|
    scope.preload_blueprint(blueprint, view)
  end
end

Very curious to hear back, either about this kind of extension or extensions in general. Thoughts I've been having are:

• Building a formal reflection API vs switching existing attrs/methods from private to public?
• Are there other obvious kinds of extensions people would want to build? (Preloading for other ORMs, doc generators, etc?)

[sandstrom]

Sounds like a good idea!

Apart from preloading, doc generation (which you've also mentioned) is a good candidate. Another one would be generating fixtures dynamically (for use in client-side tests).

[njbbaer]

@jhollinger Can this issue be closed with the introduction of #357 and #358?

[jhollinger]

A reflection API was added in 1.0; closing.