elixir - Limit fields of JSON response -

i'm using phoenixframework , library poison. current i'm working on rest api. need encode model book in 2 different ways.

1. in list of books base informations (get /books)
2. in detailed view informations (get /book/1)

get /books

{   "books": [     {       "id": 1,       "name": "book one"     },     {       "id": 2,       "name": "book two"     },     // ...   ] } 

get /books/1

{   "book": {      "id": 1,      "name": "book one",      "description": "this book one.",      "author": "max mustermann",     // ...   } } 

encoder of book

defimpl poison.encoder, for: myproject.book    @attributes [:id, :name, :description, :author]    def encode(project, _options)     project     |> map.take(@attributes)     |> poison.encode!   end end 

snippet controller

def index(conn, _params)   books = repo.all(book)   json(conn, %{books: books}) end 

how limit fields? search option :only or :exclude. has experience problem?

thanks help!

you can use render_many/4 , render_one/4:

defmodule myapp.bookview    def render("index.json", %{books: books})     render_many(books, __module__, "book.json")   end    def render("show.json", %{book: book})     render_one(book, __module__, "full_book.json")   end    def render("book.json", %{book: book})     %{       id: book.id,       name: book.name     }   end     def render("full_book.json", %{book: book})     %{       id: book.id,       name: book.name,       description: description,       author: book.author       ...     }   end end 

please note name in assigns (2nd argument of render) determined module. see render many many relationship json in phoenix framework example of using different name.

you can call controller using:

render(conn, "index.json", books: repo.all(book))  render(conn, "show.json", book: repo.get(book, 1))