Rails: redirect_to with :error, but flash[:error] empty

As stated in the Rails API only :notice and :alert are by default applied as a flash hash value. If you need to set the :error value, you can do it like this:

redirect_to show_path, flash: { error: "Insufficient rights!" }

If you are having problem to keep the flash after redirecting to another path, then use this.

flash.keep

in your method, before redirecting.