Helper functions for collaborative editing with Phoenix.Presence.
Provides utilities for tracking editing sessions, determining owner/spectator roles, and syncing state between users.
Summary
Functions
How many sessions currently have this resource open for editing.
Generates the Presence topic name for a resource.
Determines if the current socket is the owner (first in the presence list).
Gets the lock owner's metadata, or nil if no one is editing.
Gets all presences for a resource, sorted by join time (FIFO).
All presences except the lock owner, in join order.
Subscribes the current process to presence events for a resource.
Tracks the current LiveView process in a Presence topic.
Functions
How many sessions currently have this resource open for editing.
Generates the Presence topic name for a resource.
Examples
editing_topic(:entity, 5)
# => "entity_edit:5"
editing_topic(:data, 10)
# => "data_edit:10"
Determines if the current socket is the owner (first in the presence list).
Returns {:owner, presences} if this socket is the owner (or same user in different tab), or
{:spectator, owner_meta, presences} if a different user is the owner.
Examples
case get_editing_role(:entity, 5, socket.id, current_user.uuid) do
{:owner, all_presences} ->
# I can edit!
{:spectator, owner_metadata, all_presences} ->
# I'm read-only, sync with owner's state
end
Gets the lock owner's metadata, or nil if no one is editing.
Examples
case get_lock_owner(:entity, 5) do
nil -> # No one editing
meta -> # meta.user_uuid, meta.joined_at, meta.pid
end
Gets all presences for a resource, sorted by join time (FIFO).
Returns a list of tuples: [{socket_id, metadata}, ...]
Examples
get_sorted_presences(:entity, "019...")
# => [
# {"phx-abc123", %{user_uuid: "019...", joined_at: 123456, ...}},
# {"phx-def456", %{user_uuid: "019...", joined_at: 123458, ...}}
# ]
All presences except the lock owner, in join order.
Kept because it is public API — core's making-pages-live.md lists it
among this module's functions, so "no callers here" was never the whole
question. Its metadata shape did change: a meta is now user_uuid /
joined_at / pid, not the whole %User{}, because the struct carried
hashed_password to every subscriber of the topic. Read user_uuid and
load what you need.
Subscribes the current process to presence events for a resource.
After subscribing, the process will receive:
%Phoenix.Socket.Broadcast{event: "presence_diff", ...}when users join/leave
Examples
subscribe_to_editing(:entity, 5)
# Now will receive presence_diff messages
Tracks the current LiveView process in a Presence topic.
Parameters
type: The resource type (:entityor:data)id: The resource IDsocket: The LiveView socketuser: The current user struct
Examples
track_editing_session(:entity, 5, socket, user)
# => {:ok, ref}