ruby - Rescuing an ActiveRecord::RecordNotUnique in Rails 3.2 -

i new ruby , want ensure combination of 3 columns in model unique. tried using validates_uniqueness_of scopes didn't work intended. added unique index db raises activerecord::recordnotunique exception every time existing combination of values saved. problem not sure on how handle exception. in controller altered update action to:

def update     @patient_history = patienthistory.find(params[:id])    @patient_history.save!    respond_to |format|     format.html { redirect_to @patient_history, notice: 'patient history updated.' }     format.json { head :no_content }   end  rescue activerecord::recordnotunique    respond_to |format|     format.html { render action: "edit" }     format.json { render json: @patient_history.errors, status: :unprocessable_entity }     end  end end 

this code not saves changes , redirects show page of model (:patient_history) notice "patient history updated". trying controller redirect edit page , flash message @ top of page error (much validates_uniqueness of do).

thanks in advance

how did try using validates_uniqueness_of? should use make sure combination unique, this:

validates_uniqueness_of :column1, :scope => [:column2, :column3]