How do I get path parameters in LiveView?

Hentioe

My router:

live "/cities/:id/users", CityLive

I tried the handle_params function but it was never called:

def handle_params(%{"id" => id}, _uri, socket) do
  # some code
end

I tried to follow the practice in the chrismccord/phoenix_live_view_example project and still failed (session is always %{})：

def mount(%{path_params: %{"id" => id}}, socket) do
  # some code
end

Can see the parameters from the log:

Can anyone tell me what is missing?

14 comments

/phoenix #liveview

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2020-02-14 14:13:28 UTC

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LostKobrakai

If your liveview is mounted in the router and is the root one (not nested) it should work with handle_params. I did use that a few days ago. If that‘s not the case you should be able to supply the param as part of the session data you supply for live_render.

Post #1

benwilson512

Author of Craft GraphQL APIs in Elixir with Absinthe

You need to specify path_params as part of the live route session:

live "/cities/:id/users", CityLive,
  session: [:path_params]

Post #2

Hentioe

I still have not succeeded. path_params is always nil.

Post #3

chrismccord

Creator of Phoenix

You can only receive path params via the handle_params/3 callback, and handle_params is only invoked for the root LV. If you are trying to get path params to a child, you need to retrieve them from the root and pass them down to the children via assigns in the parent

Post #4

Hentioe

Maybe I misunderstood what? This is the root LV, which is not loaded from the parent LV. I can get the query parameters of the same level LV from handle_params, but I can’t get the path parameters.

The code is at:
https://github.com/elixirchina/community/blob/a86bb0c89bf158ead69d733a9d14a022ec28d6a9/lib/community_web/router.ex#L23

Thanks for the reply from the author!

Post #5

chrismccord

Creator of Phoenix

The params contain the merged path params and query param so “id” should be there. Can you provide the entire LV?

Post #6

Hentioe

I made a mistake, sorry! A very small mistake! This problem is invalid

Post #7

Hentioe

This problem does not exist because I wrote the wrong number of handle_params parameters.

Thank you all

Post #8

homanchou

I too am tripped up by this. Maybe the GitHub - chrismccord/phoenix_live_view_example · GitHub for CRUD user are out of date and need to be updated?

For example on: phoenix_live_view_example/lib/demo_web/live/user_live/show.ex


  def mount(%{path_params: %{"id" => id}}, socket) do
    if connected?(socket), do: Demo.Accounts.subscribe(id)
    {:ok, fetch(assign(socket, id: id))}
  end

will break on localhost:4000/users/1 with error: no function clause matching in DemoWeb.UserLive.Show.mount/2 because the received first arg %{} can never match %{path_params: %{"id" => id}}

If the recommendation is to now use handle_params/3 to get the path_params, (which handle_params/3 is called sometime after mount/2) does that mean that it is not possible to fetch the User data in mount/2 for the first render?

Post #9