Rails: "comparison of Array with Array failed" error

By: Pasan on 7:03 PM

Today I was trying to fix a rails app by sorting a certain list according to the alphabetical order. This list was stored in an array (let's call it value_array). And it was a pretty huge list.

I didn't know what kind of data was in this array. I only knew that the list would be in the following

value_array: {"Gamma"=>14, "Alpha"=>3, ..}

And the list will be displayed to the user as:
Gamma(14)
Alpha(3)
..
But I want this list to be in alphabetical order so that 'Alpha' would appear before 'Gamma' and so on..

I tried using the ruby array sort method.

value_array = value_array.sort { |x,y| x[0] <=> y[0] }

when I tried this on Scite ruby editor, it worked fine. But when tried on the app it failed with the error "comparison of Array with Array failed"

After about an hour of desperate struggle to find the solution, I stumbled upon this article: "Support for nil values in Enumerable.min or max"

ah.. the nil (or null if you like) object.. a common trouble creator. That is why we should always make sure are data is valid (not nil etc) i guess. So in my app, the huge list must have had some nil values. So I fixed it:

value_array = value_array.sort {|x,y| (  (y[0].nil? || x[0].nil?)  ?  0 :  (x[0] <=> y[0])  ) } 

.. all part of the long journey of learning i guess :)

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