在全球范围内允许强大的参数

Question

Is there a way to permit a param for all actions? The app I'm working on has a feature flag system and I'd like feature flags to be overridable via query string parameters (to aid testing). I've added something like the following to the application_controller :

before_action :apply_feature_flag_overrides

def apply_feature_flag_overrides
  overrides = params.permit![:feature_flags]
  current_user.feature_flag_overrides = overrides
end

This is working fine for actions that don't make use of params, but when an action does I get an error like:

ActionController::UnpermittedParameters at /upcoming_posts
found unpermitted parameter: :feature_flags

It appears that params.permit or params.require is expected to only be called once for any given action. Is that correct? Is there a way to globally white list a set of params for a cross cutting concern like this? I could update every call to params to also include :feature_flags but that's going to be error prone and repetitive.

Answer 1

Thanks to @tadman's comment about removing the param once used I got this working. The updated code looks like:

before_action :apply_feature_flag_overrides

def apply_feature_flag_overrides
  overrides = params.to_unsafe_h[:feature_flags]
  current_user.feature_flag_overrides = overrides
  params.reject! { |key| key == "feature_flags" }
end