def check_vehicle(year, make, model, submodel)
    @year = Year.find_by_year(year)
    @make = Make.find_by_make(make)
    @model = Model.find_by_model(model)
    @submodel = Submodel.find_by_submodel(submodel)
    case
    when (@year == nil or @make == nil or @model == nil or @submodel == nil)
      @vehicle_exists = 'Nil error'
    when !Year.exists?(:year => year)
      @vehicle_exists = 'Year error'
    when !Make.exists?(:make => make)
      @vehicle_exists = 'Make error'
    when !Model.exists?(:model => model)
      @vehicle_exists = 'Model error'
    when !Submodel.exists?(:submodel => submodel)
      @vehicle_exists = 'Submodel error'
      # when clause only runs when none of the varibles are nil to avoid logic error
    when !Vehicle.exists?(:year_id => @year.id, :make_id => @make.id, :model_id => @model.id, :submodel_id => @submodel.id)
        @vehicle_exists = 'Vehicle error'
    else
        @vehicle_exists = 'ok'
    end
  end