Custom JSON response format in Phoenix

Question

Phoenix seems to have an unconventional way of serializing JSON (it's new to me anyway). For example, let's say I have a table with two columns - id, and name. In nearly every other web framework the response to the show endpoint would return JSON that looks like this:

{
    "id": 1,
    "name": "foo"
}

Using the Phoenix generators the response looks like this:

{
    "data": 
    {
        "id": 1,
        "name": "foo"
    }
}

I'm seeing similar issues with POSTs, I need to post {"company": { "name": "foo" } } instead of { "name": "foo" }.

I have two questions:

Is there an advantage to serializing JSON this way that I'm unaware of?
Is there a way to handle JSON serialization in the "normal" way as described above?

With your way, how do you represent errors in the responses? — Tyler
– Tyler, Commented Sep 9, 2017 at 19:48
Clients primarily use HTTP status codes. For further detail they can look at the response body, typically this is JSON. — user140550
– user140550, Commented Sep 9, 2017 at 20:13

Phillipp · Accepted Answer · 2017-09-09 20:17:17Z

2

I think that comes down to personal preference.
You can change it of course.

In the generated view, change it from

def render("show.json", %{id: id, name: name}) do
  %{
    data: %{
      id: id,
      name: name
    }
  }
end

to

def render("show.json", %{id: id, name: name}) do
  %{
    id: id,
    name: name
  }
end

And in your controller function which accepts JSON from:

def create(conn, %{"company" => %{"name" => name}}) do
  ...
end

to

def create(conn, %{"name" => name}) do
  ...
end

Your generated functions might look different but I think you get the point.

answered Sep 9, 2017 at 20:17

Phillipp

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4 Comments

Jonas Dellinger Over a year ago

1. is not entirely true: With this approach, you will additionally have to define every column in your controller (create function), so it will be harder to maintain.

Phillipp Over a year ago

You don't have to pattern match. You can also pass the whole params map into your changeset and let it pick the keys it needs.

user140550 Over a year ago

@Phillipp this got me very close. How do I handle the signature of the update controller method since id comes from the path and company_params is from the request body? It's currently def update(conn, %{"id" => id, "company" => company_params}).

Phillipp Over a year ago

@user140550 They should be mixed together, so you can pattern match on %{"id" => id, "name" => name} for example.

user140550 · Accepted Answer · 2017-09-09 21:56:06Z

Posting diffs of Phoenix 1.3.0 generated code so that it might help others:

Controller changes

-  def create(conn, %{"company" => company_params}) do
+  def create(conn, company_params) do

-  def update(conn, %{"id" => id, "company" => company_params}) do
-    company = Repo.get!(Company, id)
+  def update(conn, company_params) do
+    company = Repo.get!(Company, conn.path_params["id"])

View changes

   def render("index.json", %{companies: companies}) do
-    %{data: render_many(companies, ConstructApi.CompanyView, "company.json")}
+    render_many(companies, ConstructApi.CompanyView, "company.json")
   end

   def render("show.json", %{company: company}) do
-    %{data: render_one(company, ConstructApi.CompanyView, "company.json")}
+    render_one(company, ConstructApi.CompanyView, "company.json")
   end

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