nathanl
Do you ever `import` inside a function?
From the docs on import:
Note that
importis lexically scoped too. This means that we can import specific macros or functions inside function definitions:
defmodule Math do
def some_function do
import List, only: [duplicate: 2]
duplicate(:ok, 10)
end
end
In the example above, the imported
List.duplicate/2is only visible within that specific function.duplicate/2won’t be available in any other function in that module (or any other module for that matter).
The example given is silly; it’s shorter and clearer to call List.duplicate(:ok, 10). But you have to import Ecto.Query to use its macros. I’ve used a function-local import when only one function in a module needs import Ecto.Query, but it’s been flagged in code review.
When, if ever, would you use import this way?
Most Liked
dimitarvp
I absolutely would and have used import Ecto.Query inside a single function, a good amount of times. Trouble is that many don’t like it for reasons they can’t explain very well themselves and deny a PR approval until the import is extracted top-side.
I partially get their point: if you get to a point where tracking the source of an imported function becomes difficult then that obviously means you should break your module apart on several smaller ones. I am a huge fan of such incremental refactorings.
But IMO some of the import-s (when not using :only) can bring in quite a lot of context that might be surprising or lead to weird compile-time warnings and runtime errors if f.ex. you import two modules and they have overlapping function names. For those cases either use :only religiously or, like you are demonstrating here – just limit the scope of the import.
It’s a very valid technique IMO. Though nowadays I lean to using :only or reducing the sizes of modules / functions more than reaching for lexically scoped import.
lud
Sometimes in a test helper in a test file I import Ecto.Query because that function is the only place where we will interact with the DB.
LostKobrakai
There’s also more more parts to lexical scopes than just function definitions. E.g. you could do an import outside of a module definition and it would affect the whole file, you could have an import within an anonymous function and it would only apply to that function, …
Personally like people before I’d also argue having a single function do an import can be perfectly fine.
Popular in Discussions
Other popular topics
Latest on Elixir Forum
Sponsor Spotlight
Move fast and fix things! Error tracking with less noise for Elixir devs who love to ship. Start your free dev account.
Categories:
Sub Categories:
Forums
Popular Tags
- #ecto
- #liveview
- #troubleshooting
- #learning-elixir
- #deployment
- #library
- #erlang
- #testing
- #genserver
- #mix
- #absinthe
- #remote-other
- #otp
- #plug
- #how-to-question
- #macros
- #postgres
- #channels
- #elixirconf
- #exunit
- #discussion
- #code-sync
- #javascript
- #podcasts
- #onsite
- #dialyzer
- #docker
- #authentication
- #umbrella
- #full-time-contract
- #podcasts-by-brainlid
- #ecto-query
- #elixir-ls
- #phoenix_html
- #iex
- #blog-post
- #graphql
- #genstage
- #ai
- #websockets
- #supervisor
- #advent-of-code
- #elixirconf-us
- #distillery
- #processes
- #forms
- #api
- #metaprogramming
- #security
- #performance
Our Sponsors
Build Elixir applications with speed and confidence.
Supporting innovation across the BEAM ecosystem.
We build reliable cloud platforms for business-critical systems.
Catch errors, track performance, monitor hosts and more.
Error tracking for Elixir devs who love to ship. Start your free account.
Producing high quality Elixir screencasts since 2017.
Enabling companies to succeed by building software people love.
The deployment platform built for Elixir: PaaS ease, VPS control.
The team behind Membrane, Popcorn, LiveDebugger. Available for hire.
Courses that'll move you from confusion to "Aha, now I get it!"