fix: Removing try/rescue. #256

api.md

@@ -310,25 +310,29 @@ defmodule AppWeb.API.ItemController do
   alias App.Item
   import Ecto.Changeset
 
-  def show(conn, params) do
-    id = Map.get(params, "id")
-
-    try do
-      item = Item.get_item!(id)
-      json(conn, item)
-    rescue
-      Ecto.NoResultsError ->
-        errors = %{
-          code: 404,
-          message: "No item found with the given \'id\'.",
-        }
-        json(conn |> put_status(404), errors)
+  def show(conn, %{"id" => id} = _params) do
+    case Integer.parse(id) do
+      # ID is an integer
+      {id, _float} ->
+        case Item.get_item(id) do
+          nil ->
+            errors = %{
+              code: 404,
+              message: "No item found with the given \'id\'."
+            }
+            json(conn |> put_status(404), errors)
+
+          timer ->
+            json(conn, timer)
+        end
 
-      Ecto.Query.CastError ->
+      # ID is not an integer
+      :error ->
         errors = %{
           code: 400,
-          message: "The \'id\' is not an integer.",
+          message: "The \'id\' is not an integer."
         }
+
         json(conn |> put_status(400), errors)
     end
   end
@@ -460,25 +464,29 @@ defmodule AppWeb.API.TimerController do
     json(conn, timers)
   end
 
-  def show(conn, params) do
-    id = Map.get(params, "id")
-
-    try do
-      timer = Timer.get_timer!(id)
-      json(conn, timer)
-    rescue
-      Ecto.NoResultsError ->
-        errors = %{
-          code: 404,
-          message: "No timer found with the given \'id\'.",
-        }
-        json(conn |> put_status(404), errors)
+  def show(conn, %{"id" => id} = _params) do
+    case Integer.parse(id) do
+      # ID is an integer
+      {id, _float} ->
+        case Timer.get_timer(id) do
+          nil ->
+            errors = %{
+              code: 404,
+              message: "No timer found with the given \'id\'."
+            }
+            json(conn |> put_status(404), errors)
+
+          timer ->
+            json(conn, timer)
+        end
 
-      Ecto.Query.CastError ->
+      # ID is not an integer
+      :error ->
         errors = %{
           code: 400,
-          message: "The \'id\' is not an integer.",
+          message: "The \'id\' is not an integer."
         }
+
         json(conn |> put_status(400), errors)
     end
   end
@@ -620,7 +628,7 @@ and serialize them as `JSON` objects
 so they can be returned to the person
 using the API! ✨
 
-## 4. Listing `timers` and validating updates
+## 4. Listing `timers` and `items` and validating updates
 
 Let's implement `list_timers/1`
 in `lib/app/timer.ex`.
@@ -638,6 +646,38 @@ Simple, isn't it?
 We are just retrieving every `timer` object
 of a given `item.id`.
 
+We are also using `Item.get_item/1`
+and `Timer.get_timer/1`, 
+instead of using 
+[bang (!) functions](https://stackoverflow.com/questions/33324302/what-are-elixir-bang-functions).
+We are not using bang functions
+because they throw Exceptions.
+And using `try/rescue` constructs
+[isn't a good practice.](https://elixir-lang.org/getting-started/try-catch-and-rescue.html)
+
+To validate parameters and return errors,
+we need to be able to "catch" these scenarios.
+Therefore, we create non-bang functions
+that don't raise exceptions.
+
+In `app/lib/timer.ex`, 
+add `get_timer/1`.
+
+```elixir
+  def get_timer(id), do: Repo.get(Timer, id)
+```
+
+In `app/lib/item.ex`, 
+add `get_item/1`.
+
+```elixir
+  def get_item(id) do
+    Item
+    |> Repo.get(id)
+    |> Repo.preload(tags: from(t in Tag, order_by: t.text))
+  end
+```
+
 Digressing,
 when updating or creating a `timer`, 
 we want to make sure the `stop` field

lib/app/item.ex

@@ -55,7 +55,7 @@ defmodule App.Item do
   end
 
   @doc """
-  Gets a single item.
+  `get_item!/1` gets a single Item.
 
   Raises `Ecto.NoResultsError` if the Item does not exist.
 
@@ -74,6 +74,25 @@ defmodule App.Item do
     |> Repo.preload(tags: from(t in Tag, order_by: t.text))
   end
 
+    @doc """
+    `get_item/1` gets a single Item.
+
+    Returns nil if the Item does not exist
+
+    ## Examples
+
+        iex> get_item(1)
+        %Timer{}
+
+        iex> get_item(1313)
+        nil
+    """
+  def get_item(id) do
+    Item
+    |> Repo.get(id)
+    |> Repo.preload(tags: from(t in Tag, order_by: t.text))
+  end
+
   @doc """
   Returns the list of items where the status is different to "deleted"
 

lib/app/timer.ex

@@ -42,7 +42,7 @@ defmodule App.Timer do
   end
 
   @doc """
-  `get_timer/1` gets a single Timer.
+  `get_timer!/1` gets a single Timer.
 
   Raises `Ecto.NoResultsError` if the Timer does not exist.
 
@@ -53,6 +53,21 @@ defmodule App.Timer do
   """
   def get_timer!(id), do: Repo.get!(Timer, id)
 
+  @doc """
+  `get_timer/1` gets a single Timer.
+
+  Returns nil if the Timer does not exist
+
+  ## Examples
+
+      iex> get_timer(1)
+      %Timer{}
+
+      iex> get_item!(13131)
+      nil
+  """
+  def get_timer(id), do: Repo.get(Timer, id)
+
   @doc """
   `list_timers/1` lists all the timer objects of a given item `id`.
 

lib/app_web/controllers/api/item_controller.ex

@@ -3,22 +3,24 @@ defmodule AppWeb.API.ItemController do
   alias App.Item
   import Ecto.Changeset
 
-  def show(conn, params) do
-    id = Map.get(params, "id")
-
-    try do
-      item = Item.get_item!(id)
-      json(conn, item)
-    rescue
-      Ecto.NoResultsError ->
-        errors = %{
-          code: 404,
-          message: "No item found with the given \'id\'."
-        }
-
-        json(conn |> put_status(404), errors)
-
-      Ecto.Query.CastError ->
+  def show(conn, %{"id" => id} = _params) do
+    case Integer.parse(id) do
+      # ID is an integer
+      {id, _float} ->
+        case Item.get_item(id) do
+          nil ->
+            errors = %{
+              code: 404,
+              message: "No item found with the given \'id\'."
+            }
+            json(conn |> put_status(404), errors)
+
+          timer ->
+            json(conn, timer)
+        end
+
+      # ID is not an integer
+      :error ->
         errors = %{
           code: 400,
           message: "The \'id\' is not an integer."

lib/app_web/controllers/api/timer_controller.ex

@@ -10,22 +10,24 @@ defmodule AppWeb.API.TimerController do
     json(conn, timers)
   end
 
-  def show(conn, params) do
-    id = Map.get(params, "id")
-
-    try do
-      timer = Timer.get_timer!(id)
-      json(conn, timer)
-    rescue
-      Ecto.NoResultsError ->
-        errors = %{
-          code: 404,
-          message: "No timer found with the given \'id\'."
-        }
-
-        json(conn |> put_status(404), errors)
-
-      Ecto.Query.CastError ->
+  def show(conn, %{"id" => id} = _params) do
+    case Integer.parse(id) do
+      # ID is an integer
+      {id, _float} ->
+        case Timer.get_timer(id) do
+          nil ->
+            errors = %{
+              code: 404,
+              message: "No timer found with the given \'id\'."
+            }
+            json(conn |> put_status(404), errors)
+
+          timer ->
+            json(conn, timer)
+        end
+
+      # ID is not an integer
+      :error ->
         errors = %{
           code: 400,
           message: "The \'id\' is not an integer."