Add Rescue From With A Separate Method as a Rails til

rails/rescue-from-with-a-separate-method.md

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+# Rescue From With A Separate Method
+
+In an earlier post on [`rescue_from`](rescue_from.md), I showed how you can
+write an exception handler with a block argument.
+
+If instead you'd prefer to implement the exception handler as a separate
+method, you can do that by passing
+[`rescue_from`](http://api.rubyonrails.org/classes/ActiveSupport/Rescuable/ClassMethods.html)
+a `with` keyword argument. This too will behave as a catch-all for a particular
+exception raised in your controller.
+
+Here is what that can look like:
+
+```ruby
+class ApplicationController < ActionController::Base
+  rescue_from User::NotAuthorized, with: :handle_unauthorized_user
+
+  def index
+    # ...
+  end
+
+  private
+
+  def handle_unauthorized_user(exception)
+    # respond with some Not Authorized page
+  end
+end
+```
+
+If the `User::NotAuthorized` exception bubbles up to the `rescue_from`, then it
+will hand that exception off to the `handle_unauthorized_user` method. We can
+include whatever logic and monitoring we want here and then render an
+appropriate response.