How to rescue by passing a block in Ruby? -

i have defined own method authorize_user in 1 of controllers, as:

    def authorize_user       if !((current_user.has_role? :admin, @operator) || (current_user.has_role? :super_admin))         raise cancan::accessdenied       end     end 

i want rescue cancan exception (or other exception matter). have used rolify in app. how rescue , redirect root_url of app custom message?

i have tried following options, none of them worked:

try 1:

rescue cancan::accessdenied |exception|     redirect_to root_url, :alert => exception.message end 

error in case: syntax error, unexpected keyword_do, expecting '('

try 2:

rescue cancan::accessdenied   redirect_to root_url, :alert => "unauthorized access" 

error in case: render and/or redirect called multiple times in action

how solve issue?

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this controller code:

class cabscontroller < applicationcontroller   before_action :set_cab, only: [:show, :edit, :update, :destroy]   before_action :authenticate_user!   after_action :authorize_user   # basic crud actions   private      def set_cab       @cab = cab.find(params[:id])       @operator = operator.find(params[:operator_id])     end       def cab_params       params.require(:cab).permit(:category, :number)     end      def authorize_user       if !((current_user.has_role? :admin, @operator) || (current_user.has_role? :super_admin))         raise cancan::accessdenied       end     end end 

i think try rescue_from method.

for example, applicationcontroller, this:

class applicationcontroller < actioncontroller::base   rescue_from cancan::accessdenied, with: :not_authorized    #other stuff          private   def not_authorized     redirect_to root_url, alert: "unauthorized access"   end end 

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since question updated more code, here additional information:

some suggestions:

• make :authorize_user before_action well. way don't need worry code running in action when user not allowed stuff.
• you might need add same :only option :set_cab since use @operator instance variable.
• last, personal code style preference have changed if ! unless increase reading flow.