Array with hash, how to merge same keys and add its value

Question

I have an array with hashes in it. If they have the same key I just want to add its value.

@receivers << result

@receivers
=> [{:email=>"[email protected]", :amount=>10.00}]
result
=> {:email=>"[email protected]", :amount=>7.00}

I want the result of above to look like this

[{:email=>"[email protected]", :amount=>17.00}]

Does anyone know how to do this?

Here is the the entire method

  def receivers
    @receivers = []
    orders.each do |order|
      product_email = order.product.user.paypal_email
      outfit_email  = order.outfit_user.paypal_email
      if order.user_owns_outfit?
        result = { email: product_email, amount: amount(order.total_price) }
      else
        result = { email: product_email, amount: amount(order.total_price, 0.9),
                   email: outfit_email,  amount: amount(order.total_price, 0.1) }
      end
      @receivers << result
    end
  end

With "same key" you mean same :email value?

Stefan
– Stefan

2016-05-03 11:57:55 +00:00
Commented May 3, 2016 at 11:57 — Stefan
– Stefan, Commented May 3, 2016 at 11:57
@Stefan, that's a good question..

dax
– dax

2016-05-03 11:59:03 +00:00
Commented May 3, 2016 at 11:59 — dax
– dax, Commented May 3, 2016 at 11:59

Santhosh · Accepted Answer · 2016-05-03 12:53:29Z

4

Using Enumerable#group_by

@receivers.group_by {|h| h[:email]}.map do |k, v|
  {email: k, amount: v.inject(0){|s,h| s + h[:amount] } }
end
# => [{:email=>"[email protected]", :amount=>17.0}]

Using Enumerable#each_with_object

@receivers.each_with_object(Hash.new(0)) {|h, nh| nh[h[:email]]+= h[:amount] }.map do |k, v|
 {email: k, amount: v}
end

edited May 3, 2016 at 12:53

answered May 3, 2016 at 12:47

Santhosh

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Comments

ecoologic · Accepted Answer · 2016-05-04 23:19:46Z

1

# Output: [{ "[email protected]" => 29.0 }, { "[email protected]" => 39.0 }]
def receivers
  return @receivers if @receivers
  # Produces: { "[email protected]" => 29.0, "[email protected]" => 39.0 }
  partial_result = orders.reduce Hash.new(0.00) do |result, order|
    product_email = order.product.user.paypal_email
    outfit_email  = order.outfit_user.paypal_email

    if order.user_owns_outfit?
      result[product_email] += amount(order.total_price)
    else
      result[product_email] += amount(order.total_price, .9)
      result[outfit_email]  += amount(order.total_price, .1)
    end

    result
  end

  @receivers = partial_result.reduce [] do |result, (email, amount)|
    result << { email => amount }
  end
end

edited May 4, 2016 at 23:19

answered May 4, 2016 at 23:14

ecoologic

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Comments

Roland Mai · Accepted Answer · 2016-05-03 12:41:39Z

0

I would just write the code this way:

def add(destination, source)
  if destination.nil?
    return nil
  end
  if source.class == Hash
    source = [source]
  end
  for item in source
    target = destination.find {|d| d[:email] == item[:email]}
    if target.nil?
      destination << item
    else
      target[:amount] += item[:amount]
    end
  end
  destination
end

usage:

@receivers = []
add(@receivers, {:email=>"[email protected]", :amount=>10.00})
=> [{:email=>"[email protected]", :amount=>10.0}]
add(@receivers, @receivers)
=> [{:email=>"[email protected]", :amount=>20.0}]

answered May 3, 2016 at 12:41

Roland Mai

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3 Comments

Stefan Over a year ago

Explicit type checking and for loops are not very idiomatic.

Roland Mai Over a year ago

well, it's not in the loop, but the idea is that you can offer different ways of calling the method

Cary Swoveland Over a year ago

It's purely stylistic, but consider return nil if destination.nil?; source = [source] if source_class == Hash. (or if Hash === source). Rather than possibly converting source to an array, you could write for item in [*source]. (That's the first time I've ever written for... :-)).

Aleksei Matiushkin · Accepted Answer · 2016-05-03 13:16:51Z

0

a = [
  {:email=>"[email protected]", :amount=>10.0},
  {:email=>"[email protected]", :amount=>7.0}
]

a.group_by { |v| v.delete :email } # group by emails
 .map { |k, v| [k, v.inject(0) { |memo, a| memo + a[:amount] } ] } # sum amounts
 .map { |e| %i|email amount|.zip e } # zip to keys
 .map &:to_h # convert nested arrays to hashes

answered May 3, 2016 at 13:16

Aleksei Matiushkin

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Comments

take · Accepted Answer · 2016-05-05 00:32:09Z

0

From what I understand, you could get away with just .inject:

a = [{:email=>"[email protected]", :amount=>10.00}]
b = {:email=>"[email protected]", :amount=>7.00}
c = {email: '[email protected]', amount: 10}

[a, b, c].flatten.inject({}) do |a, e|
  a[e[:email]] ||= 0
  a[e[:email]] += e[:amount]
  a
end

=> {
  "[email protected]" => 17.0,
  "[email protected]" => 10
}

answered May 5, 2016 at 0:32

take

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