Ecto Associations JSON displaying question

Phoenix Forum Questions / Help
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1

Hello,

I currently have 2 tables: Posts and Users. It’s a one-to-many, where a post belongs_to a user and a user has_many posts.

I am kind of stuck at the moment. I have correctly seeded the data, and have the endpoints working. I currently have user_id returning to the post table and vice-versa, but I want to return an entire entity instead of just the id in the json.

Example of what I currently have:

{
“content”: “Post Content 1”,
“id”: 97,
“is_question”: true,
“user_id”: 10
},

Example of what I would like to see:

{
“content”: “Post Content 1”,
“id”: 97,
“is_question”: true,
“user”: {
“username”: “username1234”,
“password”: “helpme”,
“posts”: [all of the user’s posts] (or have this not show is fine too)
},

I have currently tried to reconfigure my list_posts method to this:

Post
|> order_by(asc: :id)
|> preload([:user])
|> Repo.all()

and I reconfigured my view to accept User as an object. But it is erroring out and saying that the user’s posts are not loaded.

So my question: how do I preload those posts, or how can I disable it from pulling those extra fields into the extra fields for Posts User, or what’s the general advice to handle this?

Thank you, sorry for long question.

** what’s the best way to paste code in, I was having it highlight everything in the question with the three appostraphes ```?

2

The three backticks ``` (on new lines) are the best way to format code blocks IMO. When you only want to format a smaller sentence (or a single word) use the single backtick `.

3

What you want to show seems is not really related to your question. You say you want to show a post of a given user, and then show all other posts by that user? Then the preload makes no sense. It would if you would like to ouput the user with all his posts.

If you just want to show one posts and then a list of all other posts, I would handle it another way. Just fetch all posts, single out the post you want and put the rest as a property on a struct. If this is what you want I can try to make an example. Maybe even in one query.

Anyway, regarding the view, you could do it like this:

I think that you should put the preload() call after calling the Repo.all. I usually just inner_join. In your view you just need to loop over the users as well.

For example, here is the controller code:

user = User |> Repo.all() |> Preload(:posts)
render(conn, "user.json", user: user)

Then the view could be:

def render("user.json", %{user: user}) do
  %{
    id: user.id,
    username: user.username
    posts: render_may(user.posts, __MODULE__, "post.json", as: :post)       
  }
end

def render("post.json", %{post: post}) do
  %{
    id: post.id,
    content: post.content
  }
end