How to properly send JSON data to a phx phoenix API

Question

I am working on a Phoenix / phx API written using Elixir, and I am trying to test the functionality of the JSON API using Postman. I'm sending JSON data to the API to hopefully create a new user, but phx is giving me the following error.

Phoenix.ActionClauseError at POST /api/users

Not sure where the problem lies exactly, so I'll post the router and the controller for the phx project.

router.ex

defmodule KegCopRAPI.Web.Router do
  use KegCopRAPI.Web, :router

  pipeline :browser do
    plug :accepts, ["html"]
    plug :fetch_session
    plug :fetch_flash
    plug :protect_from_forgery
    plug :put_secure_browser_headers
  end

  pipeline :api do
    plug :accepts, ["json"]
    plug Guardian.Plug.VerifyHeader, realm: "Bearer"
    plug Guardian.Plug.LoadResource
  end

  scope "/", KegCopRAPI.Web do
    pipe_through :browser # Use the default browser stack

    get "/", PageController, :index
  end

  # Other scopes may use custom stacks.
  scope "/api", KegCopRAPI.Web do
    pipe_through :api

    post "/sessions", SessionController, :create
    delete "/sessions", SessionController, :delete
    post "/sessions/refresh", SessionController, :refresh

    resources "/users", UserController, except: [:show, :index, :new, :edit]
  end
end

user_controller.ex

  def create(conn, %{"user" => user_params}) do
    # with {:ok, %User{} = user} <- Accounts.create_user(user_params) do
    changeset = User.registration_changeset(%User{}, user_params)

    case Repo.insert(changeset) do
      {:ok, user} ->
        new_conn = Guardian.Plug.api_sign_in(conn, user, :access)
        jwt = Guardian.Plug.current_token(new_conn)
        # conn
        # |> put_status(:created)
        # |> put_resp_header("location", user_path(conn, :show, user))
        # |> render("show.json", user: user)
        new_conn
        |> put_status(:created)
        |> render(KegCopRAPI.SessionView, "show.json", user: user, jwt: jwt)
      {:error, changeset} ->
        conn
        |> put_status(:unprocessable_entity)
        |> render(KegCopRAPI.ChangesetView, "error.json", changeset: changeset)
    end
  end

The entire project can be found here Any and all help would greatly be appreciated.

I'm sending data to the API with the following Postman settings,

The complete error message below,

[info] POST /api/users
[debug] Processing with KegCopRAPI.Web.UserController.create/2
  Parameters: %{"email" => "foo@example.com", "password" => "[FILTERED]", "username" => "foo"}
  Pipelines: [:api]
[info] Sent 400 in 10ms
[debug] ** (Phoenix.ActionClauseError) could not find a matching KegCopRAPI.Web.UserController.create clause
to process request. This typically happens when there is a
parameter mismatch but may also happen when any of the other
action arguments do not match. The request parameters are:

  %{"email" => "foo@example.com", "password" => "password", "username" => "foo"}

    (kegcopr_api) lib/kegcopr_api/web/controllers/user_controller.ex:14: KegCopRAPI.Web.UserController.create(%Plug.Conn{adapter: {Plug.Adapters.Cowboy.Conn, :...}, assigns: %{}, before_send: [#Function<1.33581574/1 in Plug.Logger.call/2>, #Function<0.72433304/1 in Phoenix.LiveReloader.before_send_inject_reloader/2>], body_params: %{"email" => "foo@example.com", "password" => "password", "username" => "foo"}, cookies: %Plug.Conn.Unfetched{aspect: :cookies}, halted: false, host: "localhost", method: "POST", owner: #PID<0.2357.0>, params: %{"email" => "foo@example.com", "password" => "password", "username" => "foo"}, path_info: ["api", "users"], path_params: %{}, peer: {{127, 0, 0, 1}, 59852}, port: 4000, private: %{KegCopRAPI.Web.Router => {[], %{}}, :guardian_default_resource => nil, :phoenix_action => :create, :phoenix_controller => KegCopRAPI.Web.UserController, :phoenix_endpoint => KegCopRAPI.Web.Endpoint, :phoenix_format => "json", :phoenix_layout => {KegCopRAPI.Web.LayoutView, :app}, :phoenix_pipelines => [:api], :phoenix_router => KegCopRAPI.Web.Router, :phoenix_view => KegCopRAPI.Web.UserView, :plug_session_fetch => #Function<1.131660147/1 in Plug.Session.fetch_session/1>}, query_params: %{}, query_string: "", remote_ip: {127, 0, 0, 1}, req_cookies: %Plug.Conn.Unfetched{aspect: :cookies}, req_headers: [{"cache-control", "no-cache"}, {"postman-token", "da608739-758b-40d7-bdef-23b3c2a63bed"}, {"content-type", "application/json"}, {"user-agent", "PostmanRuntime/3.0.11-hotfix.2"}, {"accept", "*/*"}, {"host", "localhost:4000"}, {"accept-encoding", "gzip, deflate"}, {"content-length", "76"}, {"connection", "keep-alive"}], request_path: "/api/users", resp_body: nil, resp_cookies: %{}, resp_headers: [{"cache-control", "max-age=0, private, must-revalidate"}, {"x-request-id", "slfdhshckenp3dinlqr22m5nlakhoaq4"}, {"access-control-allow-origin", "*"}, {"access-control-expose-headers", ""}, {"access-control-allow-credentials", "true"}, {"vary", ""}], scheme: :http, script_name: [], secret_key_base: "fIEpvi5ujSQEKgmkRpt83KiLPq068sSmvFKlWFZyNpi3nkNmUtYO24Em6cXIUblZ", state: :unset, status: nil}, %{"email" => "foo@example.com", "password" => "password", "username" => "foo"})
    (kegcopr_api) lib/kegcopr_api/web/controllers/user_controller.ex:1: KegCopRAPI.Web.UserController.action/2
    (kegcopr_api) lib/kegcopr_api/web/controllers/user_controller.ex:1: KegCopRAPI.Web.UserController.phoenix_controller_pipeline/2
    (kegcopr_api) lib/kegcopr_api/web/endpoint.ex:1: KegCopRAPI.Web.Endpoint.instrument/4
    (phoenix) lib/phoenix/router.ex:277: Phoenix.Router.__call__/1
    (kegcopr_api) lib/kegcopr_api/web/endpoint.ex:1: KegCopRAPI.Web.Endpoint.plug_builder_call/2
    (kegcopr_api) lib/plug/debugger.ex:123: KegCopRAPI.Web.Endpoint."call (overridable 3)"/2
    (kegcopr_api) lib/kegcopr_api/web/endpoint.ex:1: KegCopRAPI.Web.Endpoint.call/2
    (plug) lib/plug/adapters/cowboy/handler.ex:15: Plug.Adapters.Cowboy.Handler.upgrade/4
    (cowboy) /opt/elixir/kegcopr_api/deps/cowboy/src/cowboy_protocol.erl:442: :cowboy_protocol.execute/4

Answer 1

Since you're using the data from the map inside the "user" key, you need to put all the fields under the "user" key in the request, like this:

{
  "user": {
    "username": "foo",
    "email": "foo@example.com",
    "password": "password"
  }
}

Answer 2

In your controller you are pattern-matching

"user" => user_params 

So, you have to put the user params under the user key:

"user": {
    "email": "foo@bar.com",
    ...
}