视图中未定义的功能conn / 0

Question

I am working through the Programming Phoenix 1.4 book, and while creating my view for Users, I ran into an issue. I continually get a compile error saying

== Compilation error in file lib/rumbl_web/views/user_view.ex ==
** (CompileError) lib/rumbl_web/views/user_view.ex:3: undefined function conn/0
    (elixir) src/elixir_locals.erl:107: :elixir_locals."-ensure_no_undefined_local/3-lc$^0/1-0-"/2
    (elixir) src/elixir_locals.erl:107: anonymous fn/3 in :elixir_locals.ensure_no_undefined_local/3
    (stdlib) erl_eval.erl:670: :erl_eval.do_apply/6
    (elixir) lib/kernel/parallel_compiler.ex:208: anonymous fn/4 in Kernel.ParallelCompiler.spawn_workers/6`

when attempting to compile and run the project. Here is the view in question:

defmodule RumblWeb.UserView do
  use RumblWeb, :view
  alias Rumbl.Accounts

  def first_name(%Accounts.User{name: name}) do
    name
    |> String.split(" ")
    |> Enum.at(0)
  end

  def username(%Accounts.User{username: username}) do
    username
  end

end

If I comment out the line use RumblWeb, :view , the project compiles (although it cannot render the view for obvious reasons). I am rather new to phoenix and elixir, so this has been pretty perplexing.

Answer 1

If I add conn to the third line of views/user_view.ex :

defmodule RumWeb.UserView do
  use RumWeb, :view
  conn  #====== *** HERE ***
  alias Rum.Accounts.User

  def first_name(%User{name: name} ) do
    name
    |> IO.inspect 
    |> String.split(" ")
    |> Enum.at(0)
  end


end

I get almost the same error as you:

$ mix phx.server
Compiling 9 files (.ex)
warning: variable "conn" does not exist and is being expanded to "conn()", please use parentheses to remove the ambiguity or change the variable name
  lib/rum_web/views/user_view.ex:3


== Compilation error in file lib/rum_web/views/user_view.ex ==
** (CompileError) lib/rum_web/views/user_view.ex:3: undefined function conn/0
    (stdlib) erl_eval.erl:670: :erl_eval.do_apply/6
    (elixir) lib/kernel/parallel_compiler.ex:198: anonymous fn/4 in Kernel.ParallelCompiler.spawn_workers/6

I don't have the following in the middle of my error:

ensure_no_undefined_local/3-

but maybe that's due to differences in elixir versions.

If I put conn anywhere in rumbl_web.ex , then the error points to rumbl_web.ex --not user_view.ex . Are you posting all the output after you do $ mix phx.server ?

Are you sure you don't have two windows open with two different versions of the file user_view.ex ? I would close all your editor's windows, then reopen your project and look at user_view.ex again.

I had a weird error one time, and the solution was:

../rumbl$ rm -rf _build

then do:

../rumbl$ mix phx.server 

and mix will rebuild your project, recreating the _build directory in the process.