Where is `live_path` defined?

mattellsen · March 14, 2021, 4:19pm

Hello! I’m new to elixir/phoenix/the forum, and I’m having a hard time finding the definition of MyApp.Router.Helpers.live_path (which usually shows up as Routes.live_path since Phoenix aliases it).

I’ve used the search in hexdocs for both Phoenix and LiveView, and also in both GitHub repos. I’m guessing it’s generated by a macro or some Elixir magic, but I can’t figure it out. Any help is much appreciated.

BartOtten · March 14, 2021, 4:47pm

phoenix_live_view/helpers.ex at master · phoenixframework/phoenix_live_view · GitHub?

mattellsen · March 14, 2021, 5:03pm

Is it there? Again, I might be missing something (noob here, so if it’s in a macro or something magical I might not see it), but I’ve already looked there, and searching for “path” on that page gives me 8 results, all of which are in the docs sections.

BartOtten · March 14, 2021, 5:23pm

Sorry, wrong link. Replying from mobile which makes it not so easy to track the code. Guess LiveView uses the Phoenix router helpers generator.

github.com

phoenixframework/phoenix/blob/87595656d8a51997a03925da93d7803501d3c00c/lib/phoenix/router/helpers.ex#L96


defp build_conn_forward_path(_conn, _router, _path), do: nil

defp path_with_script(path, []) do
  path
end
defp path_with_script(path, script) do
  "/" <> Enum.join(script, "/") <> path
end

@doc """
Generates the helper module for the given environment and routes.
"""
def define(env, routes, opts \\ []) do
  # Ignore any route without helper or forwards.
  routes =
    Enum.reject(routes, fn {route, _exprs} ->
      is_nil(route.helper) or route.kind == :forward
    end)

  trailing_slash? = Enum.any?(routes, fn {route, _} -> route.trailing_slash? end)

mattellsen · March 14, 2021, 6:53pm

As I suspected, it seems quite magical to me. I still don’t really understand it, but I’m guessing that the :"#{helper}_path"s in that function somehow become live_path definitions when you use Phoenix.Router in the MyAppWeb module in your app, and maybe there’s a generated LiveController (?)

Thanks! I’ll mark that as the solution.

Since that’s a part of the API, and I’d guess it’s a pretty frequent use one for LiveView apps, should that be documented somehow? (Assuming it isn’t already there, and I just missed it) This is what seems to be the documentation of that behavior on the Phoenix.Router side: Phoenix.Router — Phoenix v1.5.8

This all started because I was trying to figure out why it worked correctly when I accidentally passed a map instead of a keyword list as the last parameter to live_path, and I couldn’t find any description of the function. The iex help just says def live_path(conn_or_endpoint, action, params).

BartOtten · March 14, 2021, 8:01pm

I guess this is why it takes a map: Live routes assign to a session instead of the conn.assigns you are familiar with from ‘dead’ routes.

a map to be merged into the session, for example: %{"my_key" => 123} . The map keys must be strings

https://hexdocs.pm/phoenix_live_view/Phoenix.LiveView.Router.html

Ps. Still at mobile so can’t examine the source.

mattellsen · March 15, 2021, 8:23am

It all makes sense now. I assumed the live_path function was inherently different from the usual route helpers, since the name was the same for all my different LiveView modules, instead of being specific, the way normal route helpers are, e.g. users_path.

Then, in the last link you shared, I read that the as option defaults to :live, and that’s why it’s always live_path.

I should have understood that from your first answer. Thanks again!