Elixir 'if' and 'and' not working as expected - ecto

Question

I have this code:
if Map.has_key?(dbShop, "id") && Map.has_key?(dbProduct, "id") do
case Api.Repo.insertProductShop(conn, dbShop.id, dbProduct.id) do
{:ok, productShop} ->
{:ok, productShop}
{:error, changeset} ->
Tuple.append(errors, "could not insert product in the Shop")
end
else
IO.puts("(dbShop, id) && Map.has_key?(dbProduct, id) failed")
IO.inspect(dbShop)
IO.inspect(dbProduct)
end
Code execution makes it into the the else clause and the logs this to the console:
(dbShop, id) && Map.has_key?(dbProduct, id) failed
%Api.Shop{__meta__: #Ecto.Schema.Metadata<:loaded, "shops">, id: 23,
latitude: -36.846691, longitude: 174.7745803, name: "Yard Bar & Eatery",
placeId: "ChIJp6DGbAdIDW0RcbnExyPHvCk"}
%Api.Product{__meta__: #Ecto.Schema.Metadata<:loaded, "products">,
brand: "baba", description: " zhzngshshhshs", id: 34, image: "no-image",
name: "Nsn", numberOfVotes: nil, rating: nil}
So we can see that dbShop and dbProduct both have an id and somehow the code execution never makes it into the if clause. What am I doing wrong with my if clause? I want check that they both have an id and if so, go inside the if clause.
Full function in router:
post "/products" do
errors = {}
postedProduct = conn.body_params
dbProduct = %{}
dbShop = %{}
case Api.Repo.insertProduct(conn, postedProduct) do
{:success, product} ->
dbProduct = product
case Api.Repo.insertProductCategories(conn, postedProduct, dbProduct.id) do
{:ok, categories} ->
{:ok, categories}
{:error, failed_operation, failed_value, changes_so_far} ->
Tuple.append(errors, "could not insert productCategories. Product already has that category")
end
{:error, changeset} ->
IO.puts("product not inserted")
Tuple.append(errors, "could not insert product. Product already existed")
IO.inspect(errors)
end
if Map.has_key?(postedProduct, "shop") do
case Api.Repo.insertShop(conn, postedProduct["shop"]) do
{:ok, shop} ->
dbShop = shop
if Map.has_key?(dbShop, :id) && Map.has_key?(dbProduct, :id) do
case Api.Repo.insertProductShop(conn, dbShop.id, dbProduct.id) do
{:ok, productShop} ->
{:ok, productShop}
{:error, changeset} ->
Tuple.append(errors, "could not insert product in the Shop")
end
else
IO.puts("(dbShop, id) && Map.has_key?(dbProduct, id) failed")
IO.inspect(dbShop)
IO.inspect(dbProduct)
end
{:error, changeset} -> # shop already exists
# Tuple.append(errors, "could not insert shop")
if Map.has_key?(dbShop, "id") && Map.has_key?(dbProduct, "id") do
case Api.Repo.insertProductShop(conn, dbShop.id, dbProduct.id) do
{:ok, productShop} ->
{:ok, productShop}
{:error, changeset} ->
Tuple.append(errors, "The product has already been added to the shop")
end
end
end
end
if tuple_size(errors) > 0 do
IO.puts("errors")
IO.inspect(errors)
conn
|> put_resp_content_type("application/json")
|> send_resp(200, Poison.encode!(%{
successs: "success",
errors: errors
}))
else
conn
|> put_resp_content_type("application/json")
|> send_resp(200, Poison.encode!(%{
successs: "success"
}))
end
end

Answer 1

Your map has an atom :id as key, not the string "id", so your if should be:
if Map.has_key?(dbShop, :id) && Map.has_key?(dbProduct, :id) do
If the value is guaranteed to be non-nil if present, you can also shorten this to:
if dbShop[:id] && dbProduct[:id] do
Accessing a value using the bracket syntax will not throw an error if the key is not present, and instead return nil, which is a falsy value in Elixir.

Answer 2

Using if in Elixir is a code smell and a hint that the code might be re-written in more explicit manner. Here I would go with Kernel.SpecialForms.with/1, and instead of:
if Map.has_key?(dbShop, :id) && Map.has_key?(dbProduct, :id) do
# true
else
# false
end
use:
with %{id: shopId} when not is_nil(shopId) <- dbShop,
%{id: prodId} when not is_nil(prodId) <- dbProduct do
# true
else
^dbProduct -> IO.puts "prodId is nil"
^dbShop -> IO.puts "shopId is nil"
end