No function clause matching UserController.create Method when POSTing

Phoenix Forum Questions / Help
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1

I am trying to post a test user account to the users table in the repo but I am getting the ‘no function clause matching’ error for some reason.

I have tried POSTing on both curl and Postman with the same results. Here is my post using CURL:
curl -H "Content-Type: application/json" -X POST -d '{"name":"test","id":"5"}' http://localhost:4000/api/users2

Another trial of CURL (in the style of the tutorial I am using - https://pamit.medium.com/building-a-restful-backend-with-elixir-phoenix-84fe390975c - uses):
curl -X POST http://localhost:4000/api/users2 -H “Content-Type: application/json” -d ‘{“accounts”: {“name”: “test”, “id”: “5"}}’

In Postman I am writing the URL with the JSON in the body:

http://localhost:4000/api/users2
{"name":"test","id":"5"}

Here is my create method which should be matching in order to add the new user account:

def create(conn, %{"user" => user_params}) do
    with {:ok, %User{} = user} <- Accounts.create_user(user_params) do
      conn
      |> put_status(:created)
      |> put_resp_header("location", Routes.user_path(conn, :show, user))
      |> render("show.json", user: user)
    end
  end
2

Your create function is not matching the parameters that you are sending via curl. A possible fix is to change the first line from:

def create(conn, %{"user" => user_params}) do

to:

def create(conn, %{"accounts" => user_params}) do

Although personally i prefer to do little to no matching in controller function heads because I find the no function clause matching not very informative. If you changed your create to function to:

def create(conn, params) do
  %{"user" => user_params} = params
  ...
end

Then you would have gotten a more informative pattern matching error.

1 Like
3

Hi Axelson, many thanks for the reply! I am pretty new to Elixir and API calling so forgive me for my naivity but I have made the changes and am now getting an ‘undefined function’ error:

CompileError
lib/bank_api_web/controllers/user_controller.ex:26: undefined function user/0
Console output is shown below.
Compiling 1 file (.ex)

== Compilation error in file lib/bank_api_web/controllers/user_controller.ex ==
** (CompileError) lib/bank_api_web/controllers/user_controller.ex:26: undefined function user/0
    (elixir 1.11.2) src/elixir_locals.erl:114: anonymous fn/3 in :elixir_locals.ensure_no_undefined_local/3
    (stdlib 3.13.2) erl_eval.erl:680: :erl_eval.do_apply/6
    (elixir 1.11.2) lib/kernel/parallel_compiler.ex:314: anonymous fn/4 in Kernel.ParallelCompiler.spawn_workers/7

THis is now my create method:

 def create(conn, params) do
    %{"accounts" => user_params} = params
    |> put_status(:created)
    |> put_resp_header("location", Routes.user_path(conn, :show, user))
    |> render("show.json", user: user)
  end
4

It does not look like the code in the blog You are following… which looks like this

def create(conn, %{"business" => business_params}) do
  with {:ok, %Business{} = business} <- Directory.create_business(business_params) do
    conn
    |> put_status(:created)
    |> put_resp_header("location", business_path(conn, :show, business))
    |> render("show.json", business: business)
  end
end

Anyway, I would not recommend to follow this (old) post because things have changed since.

Maybe try this one, which cover Phoenix 1.5

BTW You are using user variable, which was never defined, and You define user_params, which is never used.

2 Likes
5

Hi, thanks for your help. I have gone through the tutorial you suggested but find myself at the stage stage once more of trying to POST to my create_user route.

Here is my create function:

def create(conn, %{"user" => user_params}) do
    with {:ok, %User{} = user} <- Account.create_user(user_params) do
      conn
      |> put_status(:created)
      |> put_resp_header("location", Routes.user_path(conn, :show, user))
      |> render("show.json", user: user)
    end
  end

And this is the error in Postman:

no function clause matching in SpBankWeb.UserController.create/2
The following arguments were given to SpBankWeb.UserController.create/2:

    # 1
    %Plug.Conn{adapter: {Plug.Cowboy.Conn, :...}, assigns: %{}, before_send: [#Function<0.11227428/1 in Plug.Telemetry.call/2>], body_params: %{"amount" => "5.0", "name" => "test2"}, cookies: %{}, halted: false, host: "localhost", method: "POST", owner: #PID<0.471.0>, params: %{"amount" => "5.0", "name" => "test2"}, path_info: ["api", "users"], path_params: %{}, port: 4000, private: %{SpBankWeb.Router => {[], %{}}, :phoenix_action => :create, :phoenix_controller => SpBankWeb.UserController, :phoenix_endpoint => SpBankWeb.Endpoint, :phoenix_format => "json", :phoenix_layout => {SpBankWeb.LayoutView, :app}, :phoenix_request_logger => {"request_logger", "request_logger"}, :phoenix_router => SpBankWeb.Router, :phoenix_view => SpBankWeb.UserView, :plug_session_fetch => #Function<1.123471702/1 in Plug.Session.fetch_session/1>}, query_params: %{}, query_string: "", remote_ip: {127, 0, 0, 1}, req_cookies: %{}, req_headers: [{"accept", "*/*"}, {"accept-encoding", "gzip, deflate, br"}, {"connection", "keep-alive"}, {"content-length", "31"}, {"content-type", "application/json"}, {"host", "localhost:4000"}, {"postman-token", "dba91f4a-d119-4ce9-a866-4be4fcc2a5b8"}, {"user-agent", "PostmanRuntime/7.26.8"}], request_path: "/api/users", resp_body: nil, resp_cookies: %{}, resp_headers: [{"cache-control", "max-age=0, private, must-revalidate"}, {"x-request-id", "FkraqL6-WjCGiuEAAACh"}], scheme: :http, script_name: [], secret_key_base: :..., state: :unset, status: nil}

    # 2
    %{"amount" => "5.0", "name" => "test2"}
6

SOLVED: Inside the body of the HTML post on Postman, you need to include the exact variable name that the controller function uses (in my case this is ‘user’).

{“user”:{“name”:“test2”,“amount”:“5.0”}}

^^ This worked!

Thanks all who helped