Update map in loop

experimentix

Hello

I’m new to elixir and i’m struggling with this problem

I’ve a map lets call it order and that has several products

I want to loop through this products map inside the order map and append some info from another map called associated products

it looks like this

orders map

%{
    "_csrf_token" => "gwsgw",
    "custom_tags" => "",
    "id" => "62212",
    "products" => %{
      "123456" => %{
        "category" => "3",
        "tag" => ["hero", "superstar"],
        "title" => "Product title"
      },
      "234567" => %{"category" => "5", "title" => "Product title"},
	  
      "345678" => %{
        "category" => "8",
        "tag" => ["creation", "dynasty"],
        "title" => "Product title"
      },
      "456789" => %{
        "category" => "5",
        "title" => "Product title"
      },
    },
    "order_id" => "193885",
    "custom_message" => "Nothing to declare",
    "tags_title" => %{"tag" => ["preview"]},
    "allcats" => "5"
  }

associated products map

%{
  "123456" => [
    %{
      "id" => "4984944",
      "has_stock" => false,
      "name" => "Other product Name",
      "product_id" => "123456",
     
    },
    %{
      "id" => "3511064",
      "has_stock" => true,
      "name" => "Other product Name",
      "product_id" => "123456",
     
    }
  ],
  "234567" => [
    %{
      "id" => "3511075",
      "has_stock" => true,
      "name" => "Other product Name",
      "product_id" => "234567",
     
    },
    %{
      "id" => "3511076",
      "has_stock" => false,
      "name" => "Other product Name",
      "product_id" => "234567",
     
    }
  ],
  "345678" => [
    %{
      "id" => "3511082",
      "has_stock" => true,
      "name" => "Other product Name",
      "product_id" => "345678",
     
    },
    %{
      "id" => "3511083",
      "has_stock" => false,
      "name" => "Other product Name",
      "product_id" => "345678",
     
    }
  ]

}

i tried this code to put the associated products but it only gets updated with the last item, i assume its because it doesn’t update the order in every loop

order = for {pid, v} <- order["products"] do
        IO.inspect pid
        IO.inspect v

      order = put_in(order, ["products", pid,"associated_products"], associated_products[pid])

      end

How can i achieve this result??

%{
    "_csrf_token" => "gwsgw",
    "custom_tags" => "",
    "id" => "62212",
    "products" => %{
      "123456" => %{
        "category" => "3",
        "tag" => ["hero", "superstar"],
        "title" => "Product title",
		"associated_products" => [
			%{
			  "id" => "4984944",
			  "has_stock" => false,
			  "name" => "Other product Name",
			  "product_id" => "123456",
			 
			},
			%{
			  "id" => "3511064",
			  "has_stock" => true,
			  "name" => "Other product Name",
			  "product_id" => "123456",
			 
			}
		  ]
		
      },
      "234567" => %{"category" => "5",
		  "title" => "Product title",
		  "associated_products" => [
				%{
				  "id" => "4984944",
				  "has_stock" => false,
				  "name" => "Other product Name",
				  "product_id" => "234567",
				 
				},
				%{
				  "id" => "3511064",
				  "has_stock" => true,
				  "name" => "Other product Name",
				  "product_id" => "234567",
				 
				}
			  ]
	  },
	  
      "345678" => %{
        "category" => "8",
        "tag" => ["creation", "dynasty"],
        "title" => "Product title",
		"associated_products" => [
			%{
			  "id" => "4984944",
			  "has_stock" => false,
			  "name" => "Other product Name",
			  "product_id" => "345678",
			 
			},
			%{
			  "id" => "3511064",
			  "has_stock" => true,
			  "name" => "Other product Name",
			  "product_id" => "345678",
			 
			}
		  ]
      },
      "456789" => %{
        "category" => "5",
        "title" => "Product title",
		"associated_products" => [
			%{
			  "id" => "4984944",
			  "has_stock" => false,
			  "name" => "Other product Name",
			  "product_id" => "456789",
			 
			},
			%{
			  "id" => "3511064",
			  "has_stock" => true,
			  "name" => "Other product Name",
			  "product_id" => "456789",
			 
			}
		  ]
      },
    },
    "order_id" => "193885",
    "custom_message" => "Nothing to declare",
    "tags_title" => %{"tag" => ["preview"]},
    "allcats" => "5"
  }

5 comments

#comprehensions #loop #map

0 2158 5

2022-04-14 11:00:35 UTC

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stefanluptak

Check this gist: update_map_in_loop.md · GitHub
It’s a Livebook, so you can copy and paste it into your Livebook server and play with it.

If you need more explanation, I can provide it. I am pretty sure there are more elegant ways to achieve this, but this should be good enough as a start.

The problem with your solution is that it’s not “reducing” the order (keeping the changes for all iterations), just returning the list of modified orders. Each order (item of the returned list) is the order modified but just for a single product.

Hope this helps a bit.

Post #1

experimentix

Thank you very much, it worked. And thanks for small explanation.

I think i understand how things work now looking at your code.

Once again thanks

Post #2

experimentix

Since my associated products has the key same as the product key i ended with removing some of your code and referencing it like this

Enum.reduce(order["products"], order, fn {product_id, _product}, order ->
   update_in(order, ["products", product_id], fn product ->
    Map.put(product, "associated_products", associated_products[product_id])
  end)
end)

Once again thanks

Post #3

ConstantBall

This will give a value of nil to "associated_products" if the product_id doesn’t exist in the associated_products map. Is that the behaviour you want? Are you looking to set another default value if that’s the case? Or do you only want to insert "associated_products" into order["products"][product_id] if associated_products[product_id] exists?