bianchidotdev
I came across a blog post that implemented a function guard for a liveview socket connection’s presence. It seems like a really ergonomic way to separate out mount functions for connected sockets and disconnected sockets, and I was surprised I wasn’t able to find any existing proposals or suggestions to implement connected? as a macro (very possibly my search fu failing me).
Is there any appetite in implementing this function guard in core liveview? Are there reasons it’s not implemented as a guard yet.
Code referenced in the blog post:
defguard is_connected?(socket) when socket.transport_pid != nil
Enabling:
def mount(params, session, socket) when is_connected?(socket) do
# Connected mount
end
def mount(params, session, socket) do
# Disconnected mount
end
Where Next?
Trending in Proposals: Ideas
Other Trending Topics
Latest Phoenix Threads
Latest on Elixir Forum
Sponsor Spotlight
Bringing learning, work and compliance together since 1987.
Categories:
Sub Categories:
Forums
Popular Tags
- #ecto
- #liveview
- #troubleshooting
- #learning-elixir
- #library
- #deployment
- #erlang
- #testing
- #genserver
- #mix
- #absinthe
- #remote-other
- #otp
- #plug
- #how-to-question
- #macros
- #postgres
- #elixirconf
- #channels
- #exunit
- #discussion
- #code-sync
- #podcasts
- #javascript
- #onsite
- #dialyzer
- #docker
- #authentication
- #ai
- #umbrella
- #full-time-contract
- #podcasts-by-brainlid
- #blog-post
- #ecto-query
- #elixirconf-us
- #elixir-ls
- #phoenix_html
- #iex
- #graphql
- #genstage
- #websockets
- #supervisor
- #advent-of-code
- #distillery
- #processes
- #elixirconf-eu
- #api
- #forms
- #security
- #hex
Our Sponsors
Build Elixir applications with speed and confidence.
Supporting innovation across the BEAM ecosystem.
We build reliable cloud platforms for business-critical systems.
Error tracking, logs, uptime, and Just Enough APM. Built for developers.
Elixir, Erlang & BEAM conferences from Code Sync - join us in 2026!
Practical resources that improve the lives of professional developers.
Master modern tools, write cleaner code, and tackle real-world challenges.
Bringing learning, work and compliance together since 1987.
The team behind Membrane, Popcorn, LiveDebugger. Available for hire.
Courses that'll move you from confusion to "Aha, now I get it!"
Showing Posts 1 to 5- Show Best Posts
- Show All (oldest first)
- Show All (newest first)
al2o3cr
One reason this may not exist already - the
map.fieldnotation wasn’t supported in guards until this PR, released in 1.11:https://github.com/elixir-lang/elixir/pull/9711
Phoenix 1.6 only requires Elixir 1.9+, so Phoenix 1.7 is the earliest version this guard could have been included in.
D4no0
definetly some new feature I didn’t see yet
JohnnyCurran
Glad you liked the article! I have been thinking about making a PR to add it to LiveView. I wanted to get some feedback on it first. I suppose this thread might serve that purpose
I haven’t tested it, but I imagine the map.field syntax could be worked around by matching on the fields in the struct:
But that’s just a guess. I wrote that in the forum post editor
codeanpeace
Gave it a whirl and it doesn’t look like you can pattern match when defining guards:
** (ArgumentError) invalid syntax in defguard is_connected?(%Socket{transport_pid: transport_pid})JohnnyCurran
Thanks for giving it a shot though!
I guess that makes sense because guards have to be compile time constants and pattern matching is not