CODEWITHSUNDEEP
ruby-on-railsrubyloopsunique
Michael
Michael

Reputation: 921

each loop: show item once and sum quantity

I currently am using this peice of code to loop through ordered items for a specific date

<tr>
  <th>Item</th>
  <th>Quantity</th>
</tr>
<% @demand.each do |d| %>
  <% d.demand_items.each do |item| %>
    <tr>
      <td><%= item.item.name %></td> 
      <td><%= @item_count %></td>
    </tr>
  <% end %>
<% end %>

Currently if item 1 is ordered more than once, it shows up multiple times in the list. I just want it to show up once and have a number next to it to show how many are ordered. For example, if item_1 has a quantity of 5 in demand_1 and item_1 has a quantity of 10 in demand_2, the result should be:

item_1 .... 15

Thanks!

Upvotes: 3

Views: 852

Answers (2)

MrYoshiji
MrYoshiji

Reputation: 54882

This should do it:

<tr>
  <th>Item</th>
  <th>Quantity</th>
</tr>
<% @demand.flat_map(&:demand_items).group_by(&:item).each do |item, demands| %>
  <tr>
    <td><%= item.name %></td>
    <td><%= demands.map(&:quantity).inject(:+) %></td>
  </tr>
<% end %>

Hope this helps!

Some explanation:

@demand.flat_map(&:demand_items)
# equivalent: (long version)
@demand.map{ |demand| demand.demand_items }.flatten
# retrieves all demand_items of each demand in the @demand list
# flatten the result (which is a double-dimension array)

demands.map(&:quantity)
# sends .quantity call to each element of the demands list
# and put it in an array (so this returns an array of quantity of each demand)
# equivalent: (long version)
demands.map{ |demand| demand.quantity }

demands.map(&:quantity).inject(:+)
# the inject(:+) will inject the method + (add) between each element of the array
# since the array is a list of quantities
# the inject(:+) sums each quantity of the list

Upvotes: 3

Michael Durrant
Michael Durrant

Reputation: 96504

I would try and get the uniq items and then count them while looping, something like:

(@demand.demand_items.sort.uniq).each do |d|
  d.item_name
  d.demand_items.count
end

This is untested pseudo code.

Upvotes: 2

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