Handling error in Phoenix/Elixir

1
votes

1) How can I handle "server error" and "page not found" on the application level? Where should I put a handler which renders appropriate pages?

That is, if a user goes to "my_website.com/fdafdsafds" -- how can I render the page "error/my_custom_404_page.html" to him?

Or if somewhere in my app an error occurs such as "1 / 0", how can I catch it on the application level?

2) Inside a plug I have this:

  def call(conn, opts) do
    if !some_condition do
      # ....
    else
      # how to render an html template?
      Conn.send_resp(conn, 401, "access denied") |> Conn.halt()
    end
  end

How can I render my custom error html template from "error/my_html_template.html" and pass parameters to it?

2
elixirphoenix-framework

2 Answers

2
votes

TL;DR You are to declare custom exceptions (with standard Elixir defexception macro) and to implement Plug.Exception protocol for them, like this:

defimpl Plug.Exception, for: Ecto.NoResultsError do
  def status(_exception), do: 418
end

Then, once raised, it will be handled by this implementation.

There is a detailed description on how to do this in Phoenix documentation. I do not see any reason to copy the content from there, but I must admit the explanation is pretty straightforward.

0
votes

1) How can I handle "server error" and "page not found" on the application level? Where should I put a handler which renders appropriate pages?

I used following trick

scope "/", MyApp do  
  post "/*path",  PageController, :invalid_path  
  put "/*path",  PageController, :invalid_path  
  get "/*path",  PageController, :invalid_path  
end

And define custom error message in invalid_path method.

NOTE: Add these lines at end of the router file