Fix Missing Import in Elixir

Missing Import Errors in Elixir

Elixir uses alias, import, use, and require — each with different purposes. The error (UndefinedFunctionError) function X.y/1 is undefined usually means a missing import or dependency.

alias vs import vs use

# alias — shortens module names
alias MyApp.Accounts.User
User.changeset(attrs)  # Instead of MyApp.Accounts.User.changeset(attrs)

# import — brings functions into current scope
import Ecto.Query, only: [from: 2, where: 3]
from(u in User, where: u.active == true)

# use — invokes the module's __using__ macro
use GenServer  # Injects GenServer callbacks

Missing Dependency

If a module isn't found at all, it might be a missing dependency:

# mix.exs
defp deps do
  [
    {:phoenix, "~> 1.7"},
    {:jason, "~> 1.4"},  # Add missing dep
  ]
end

Then run:

mix deps.get
mix compile

Module Not Compiled

If you get module X is not available, the module might have a compilation error:

mix compile --force

Require for Macros

# Macros need require, not import
require Logger
Logger.info("This works")

# Without require:
Logger.info("This fails")  # (CompileError) you must require Logger

Phoenix-Specific

# In Phoenix controllers, use brings in helpers
use MyAppWeb, :controller  # Imports controller helpers
use MyAppWeb, :live_view    # Imports LiveView helpers

Bugsly captures UndefinedFunctionError and CompileError in Elixir apps with the full module path, making it easy to trace which import is missing.