Question

I’m doing a whole bunch of stuff with an array of hashes, and learning a ton.

I am trying to loop through the array and change some of the values, and remove some, etc. etc.

I think that because I’m using things like

    find_best = original_array.select{|h| h[:score]>15}

I’m ending up with a new array of the matches, rather than a bunch of pointers to the original array.

So when I say (as example)

   find_best.each do |something|
            #manipulate somehow
   end

Those changes are not reflected in the original_array.

I guess I could merge the find_best into the original_array, though I’m not entirely sure how to do that, or if that is the right thing to do.

The biggest problem I run into is when I say

 while find_best.length>0
       #do some stuff that recalculates find_best
        find_best = original_array.select{|h| h[:score]>15} #so I'm resetting the loop for find_best and exit if all the work is done. 
 end

Answer 1

As Niklas already noted in the comment, select, map and alike create new arrays, but they contain the very objects from the original array, not their copies.

Observe:

a = [{foo: 1, bar: 'a'}, {foo: 3, bar: 'b'}, {foo: 2, bar: 'c'}]
#=> [{:foo=>1, :bar=>"a"}, {:foo=>3, :bar=>"b"}, {:foo=>2, :bar=>"c"}]
a.max_by{|e| e[:foo]}[:bar] = 'GOTCHA!'
a
#=> [{:foo=>1, :bar=>"a"}, {:foo=>3, :bar=>"GOTCHA!"}, {:foo=>2, :bar=>"c"}]

See? A member of the original array was modified.