300, :quantity=>1}, {:shipping_id=>3, :...">
Geek asks and answers

Grouping through an item in a hash

Suppose I have this array

x=[{:shipping_id=>2, :fsn=>"ab", :price=>300, :quantity=>1},
   {:shipping_id=>3, :fsn=>"abc",:price=>500, :quantity=>2},
   {:shipping_id=>2, :fsn=>"abcd",:price=>300,:quantity=>3},
   {:shipping_id=>4, :fsn=>"abx", :price=>600,:quantity=>1},
   {:shipping_id=>3, :fsn=>"abb", :price=>400,:quantity=>1}]

I want to group it by a unique delivery identifier, but in this case, let's just group by shipping_id = 2

So I do x.select! {|y| y[:shipping_id]==2}, which gives me

[{:shipping_id=>2, :fsn=>"ab",:price=>300,:quantity=>1}, {:shipping_id=>2, :fsn=>"abcd",:price=>300,:quantity=>3}]

But the problem is that I want to get the result in this form

x={:shipping_id=>[2,2],:fsn=>["ab","abcd"],:price=>[300,300],:quantity=>[1,3]}

What should I do? I can do this in a few lines, but is there an optimized way for this?

UPDATE -: Final working solution (My decision) -

controller

 new_params={}
 order_hash.each do |row|
        new_params=row.convert_to_params(new_params)
 end
 params.merge!(new_params)

Model

 def convert_to_params(new_params)
    item=self.instance_values.symbolize_keys
    item.each do |k, v|
      new_params[k].nil? ? new_params[k]=[v] : new_params[k].push(v)
    end
    return new_params
 end

It gave me my desired result.

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3 answers
arr = x= [{:shipping_id=>2, :fsn=>"ab"}, 
{:shipping_id=>3, :fsn=>"abc"}, {:shipping_id=>2, :fsn=>"abcd"}, 
{:shipping_id=>4, :fsn=>"abx"}, {:shipping_id=>3, :fsn=>"abb"}]
@h = {}
arr.group_by {|x| x[:shipping_id]==2 }[true].inject({}) do |mem,i|
   i.each{|k,v| mem[k] =  [v] << mem[k] ; @h = mem}
end
p @h #=> {:shipping_id=>[2, 2], :fsn=>["abcd", "ab"]}
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You can do:

ret = Hash[x.group_by {|e| e[:shipping_id]}.map {|e| [e.first, e.last.map {|t| t[:fsn]}]}]

and then if you only need those for shipping_id = 2

> ret[2]
=> ["ab", "abcd"]
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:

>> z = x.group_by {|y| y[:shipping_id] }
#=> {2=>[{:shipping_id=>2, :fsn=>"ab"}, {:shipping_id=>2, :fsn=>"abcd"}], 3=>[{:shipping_id=>3, :fsn=>"abc"}, {:shipping_id=>3, :fsn=>"abb"}], 4=>[{:shipping_id=>4, :fsn=>"abx"}]}

>> Hash[z.map {|k, v| Array[[k]*v.count, v] }]
#=> {[2, 2]=>[{:shipping_id=>2, :fsn=>"ab"}, {:shipping_id=>2, :fsn=>"abcd"}], [3, 3]=>[{:shipping_id=>3, :fsn=>"abc"}, {:shipping_id=>3, :fsn=>"abb"}], [4]=>[{:shipping_id=>4, :fsn=>"abx"}]}

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