Sum of hash value inside the array In ruby

Question

I have array like this

data = 
  [
    { :lineItemKey=>57, :sku=>"12GA-RIO",  
      :name=>"12 Gauge", :quantity=>4, :unitPrice=>5.76 },
    { :lineItemKey=>168, :sku=>"22LR-CAS-40-CPRN-50", 
      :name=>"22 Long", :quantity=>2, :unitPrice=>7.6 },
    { :lineItemKey=>57, :sku=>"12GA-RIO", 
      :name=>"12 Gauge", :quantity=>1, :unitPrice=>5.76 }, 
    { :lineItemKey=>236, :sku=>"300BLK-UNWD-CTC-220-BTHP-20",
      :name=>"300 BLK", :quantity=>1, :unitPrice=>31.2 }
  ]

I need to sum the quantity if the sku is same and remove the duplicate. so the output should be like:

data = 
  [
    { :lineItemKey=>57, :sku=>"12GA-RIO", 
      :name=>"12 Gauge", :quantity=>5, :unitPrice=>5.76 },
    { :lineItemKey=>168, :sku=>"22LR-CAS-40-CPRN-50", 
      :name=>"22 Long", :quantity=>2, :unitPrice=>7.6 }, 
    { :lineItemKey=>236, :sku=>"300BLK-UNWD-CTC-220-BTHP-20",
      :name=>"300 BLK", :quantity=>1, :unitPrice=>31.2 }
  ]

Cary Swoveland · Accepted Answer · 2022-01-13 07:00:27Z

2

data.each_with_object({}) do |g,h|
  h.update(g[:lineItemKey]=>g) do |_k, old_hash, new_hash|
    old_hash.merge(quantity: old_hash[:quantity] + new_hash[:quantity])
  end
end.values
  #=> [
  # {:lineItemKey=>57, :sku=>"12GA-RIO", :name=>"12 Gauge",
  #  :quantity=>5, :unitPrice=>5.76},
  # {:lineItemKey=>168, :sku=>"22LR-CAS-40-CPRN-50", :name=>"22 Long",
  #  :quantity=>2, :unitPrice=>7.6},
  # {:lineItemKey=>236, :sku=>"300BLK-UNWD-CTC-220-BTHP-20",
  #  :name=>"300 BLK", :quantity=>1, :unitPrice=>31.2}
  # ]

Note that the receiver of values is

{
   57=>{:lineItemKey=>57, :sku=>"12GA-RIO", :name=>"12 Gauge",
        :quantity=>5, :unitPrice=>5.76},
  168=>{:lineItemKey=>168, :sku=>"22LR-CAS-40-CPRN-50",
        :name=>"22 Long", :quantity=>2, :unitPrice=>7.6},
  236=>{:lineItemKey=>236, :sku=>"300BLK-UNWD-CTC-220-BTHP-20",
        :name=>"300 BLK", :quantity=>1, :unitPrice=>31.2}
}

This uses the form of Hash#update (a.k.a merge!) that employs a block to compute the values of keys that are present in both hashes being merged. Here that block is

do |_k, old_hash, new_hash|
  old_hash.merge(quantity: old_hash[:quantity] + new_hash[:quantity])
end

See the doc for definitions of the three block variables. The underscore preceding k (the common key) is intended tro signal to the reader that it is not used in the block calculation (a common convention which is often just the underscore alone).

edited Jan 13, 2022 at 7:00

answered Jan 13, 2022 at 6:55

Cary Swoveland

111k6 gold badges69 silver badges105 bronze badges

Sign up to request clarification or add additional context in comments.

2 Comments

Rajagopalan Over a year ago

old_hash.merge(quantity: old_hash[:quantity] + new_hash[:quantity]) this line has to be executed only when keys are equal, eh? But that checking is not found within your program, but still it works, how? Could you please help me understand?

Cary Swoveland Over a year ago

@Rajagopalan, recall that the block is executed only when the “old” and “new” hashes being merged have same key (g[:lineItemKey]).

Chris · Accepted Answer · 2022-01-13 07:48:32Z

1

Input

data = 
  [
    { :lineItemKey=>57, :sku=>"12GA-RIO", 
      :name=>"12 Gauge", :quantity=>4, :unitPrice=>5.76 },
    { :lineItemKey=>168, :sku=>"22LR-CAS-40-CPRN-50", 
      :name=>"22 Long", :quantity=>2, :unitPrice=>7.6 },
    { :lineItemKey=>57, :sku=>"12GA-RIO", 
      :name=>"12 Gauge", :quantity=>1, :unitPrice=>5.76 }, 
    { :lineItemKey=>236, :sku=>"300BLK-UNWD-CTC-220-BTHP-20",
      :name=>"300 BLK", :quantity=>1, :unitPrice=>31.2 }
  ]

Code

p data.group_by { |x| x[:lineItemKey] }
      .values
      .map { |arr| arr.reduce { |h1, h2| h1.merge(h2) { |k, oldv, newv| k.eql?(:quantity) ? oldv += newv : oldv } } }

Output

[
  { :lineItemKey=>57, :sku=>"12GA-RIO", 
    :name=>"12 Gauge", :quantity=>5, :unitPrice=>5.76 }, 
  { :lineItemKey=>168, :sku=>"22LR-CAS-40-CPRN-50",  
    :name=>"22 Long", :quantity=>2, :unitPrice=>7.6 }, 
  { :lineItemKey=>236, :sku=>"300BLK-UNWD-CTC-220-BTHP-20", 
    :name=>"300 BLK", :quantity=>1, :unitPrice=>31.2 }
]

edited Jan 13, 2022 at 7:48

Chris

38.2k6 gold badges33 silver badges59 bronze badges

answered Jan 13, 2022 at 5:04

Rajagopalan

6,0943 gold badges15 silver badges33 bronze badges

4 Comments

sourabh Over a year ago

Rajagopalan looks good! just } is missing at the end, let me try.

Rajagopalan Over a year ago

You are right, I missed the } while I am copying from my editor. Now I have added.

Cary Swoveland Over a year ago

Looks good! (I remember when you were a kid.) I would say that rather than too few braces you have too many. It would be easier to read with some do ... end's.

Rajagopalan Over a year ago

@CarySwoveland Thanks! I thought of using it but I wanted to have everything in single line so used the { instead of using do end

Collectives™ on Stack Overflow

Sum of hash value inside the array In ruby

2 Answers 2

2 Comments

4 Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

2 Comments

4 Comments

Your Answer

Sign up or log in

Post as a guest

Related