Best Way to Handle Unexpected Database Nils

Question

I am working with a third party API and it seems like it unexpectedly returns null fields for what should be numeric attributes.

My application is using a lot of Model.whatever_attribute checks throughout its views and I suddenly started to get errors like "undefined method `>' for nil:NilClass" and similar errors where whatever_attribute is nil.

I have view code like this for example:

.stat{ :class => ((@obj.value > 1.2 and @obj.vaue > 0) ? 'green-font': 'red-font')}

Which comes back with the aforementioned exception if value = nil.

Now, I cannot really assume value to be 0 and have a default in the database for that, because it could be the wrong value. I would have to test whether I got null back from the API and maybe present a "N/A" or "-" to the end user.

I can do that all sorts of ways of course, my initial thinking was to setup a helper method and pretty much do the nil? check in there and return accordingly, but I am wondering.

Is there some sort of ruby idiom that can be used to handle such situations more gracefully ?

Answer 1

I think it must be a model-based method

In app/models file model_name.rb

Method like:

def get_font_class
  self.value.nil? || self.value < 0 ? "green-font" : "red-font"
end

You can add any checks you want
NOTE: || checks first expression(self.value.nil?) and if it's true dont's checks the second(self.value < 0)

And in view use this method:

class: @model_object.get_font_class