Sort an array and make it unique on multiple conditions - Ruby

Question

This is a sample array example as Input :

hashForAnimals = [{ 
    :animalCd=>"Tiger",:animalType=>"Carnivore", :sortOrder =>3},
    {:animalCd=>"Cow",:animalType=>"Herbivore", :sortOrder =>5},
    {:animalCd=>"Rabbit", :animalType=>"Herbivore", :sortOrder =>2}, 
    {:animalCd=>"Shark",:animalType=>"Carnivore", :sortOrder =>4}, 
    {:animalCd=>"Cow",:animalType=>"Carnivore", :sortOrder =>1},
    {:animalCd=>"Bear", :animalType=>"Omnivore", :sortOrder =>7},
    {:animalCd=>"Tiger",:animalType=>"Carnivore", :sortOrder =>6}]

Expected Output:

hashForAnimals = [{
  :animalCd=>"Cow", :animalType=>"Carnivore",  :sortOrder =>1},
  {:animalCd=>"Rabbit", :animalType=>"Herbivore", :sortOrder =>2},
  {:animalCd=>"Tiger",:animalType=>"Carnivore", :sortOrder =>3},
  {:animalCd=>"Shark",:animalType=>"Carnivore", :sortOrder =>4},
  :animalCd=>"Cow", :animalType=>"Herbivore",  :sortOrder =>5}
  {:animalCd=>"Bear", :animalType=>"Omnivore", :sortOrder =>7}]

I need to sort the array on the basis of sort order and then I need to make the array unique with respect to animalCd falling under the same group i.e. animalType.

Tiger has appeared once with the minimum sort order, however Cow is appearing twice in the array but with different animalType.

It can be done by collecting the array into multiple animalType arrays and sorting and making them unique and merge back to a single array. However, I need an elegant solution for this.

Sample code that I'm trying:

hashForAnimals.sort!{|x,y| x[:sortOrder].to_i<=>y[:sortOrder].to_i}.group_by { |a| a[:animalType]}

I can group them into seperate hashes but then I need to make the individual hashes unique and then merge into the array.

Is this even possible in the way by which I'm approaching it?

Bartłomiej Gładys · Accepted Answer · 2016-09-14 18:38:06Z

3

you can use sort_by method and uniq and values_at

hashForAnimals.sort_by{ |a| a[:sortOrder] }.uniq{ |k| k.values_at(:animalCd, :animalType) }


# => [{:animalCd=>"Cow", :animalType=>"Carnivore", :sortOrder=>1}, {:animalCd=>"Rabbit", :animalType=>"Herbivore", :sortOrder=>2}, {:animalCd=>"Tiger", :animalType=>"Carnivore", :sortOrder=>3}, {:animalCd=>"Shark", :animalType=>"Carnivore", :sortOrder=>4}, {:animalCd=>"Cow", :animalType=>"Herbivore", :sortOrder=>5}, {:animalCd=>"Bear", :animalType=>"Omnivore", :sortOrder=>7}]

edited Sep 14, 2016 at 18:38

answered Sep 14, 2016 at 18:29

Bartłomiej Gładys

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7 Comments

Bartłomiej Gładys Over a year ago

Did you try my last update, with values_at method ?

remonses Over a year ago

Was unaware of values_at API. Brilliant and thanks for the prompt reply!

Cary Swoveland Over a year ago

There may be less to sort if you uniq before sort (and there's no reason to think uniq will be faster by doing it second).

Bartłomiej Gładys Over a year ago

What if i use uniq and delete element with more sortOrder ?

Cary Swoveland Over a year ago

...but my suggestion does affect which elements are selected by uniq, which may be important (don't know from the question).

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