Build relation CURD

relation.ex

#Build relation is very common in DB layer, like user and it's posts

#1> We need define the relation between Module user and posts
schema "users" do
  has_many :posts, Blog.Post
end

schema "posts" do
  belongs_to(:user, Blog.User)
end
#2> We need define the migration ops for post
def change do
  alter table(:posts) do
    add :user_id, references(:users,on_delete: :nothing)
  end
end

#3>We need add user infomation for post CURD within post controler
#3.1 Build post struct from a real user struct then construct a post changeset
def create(conn, %{"post" => post_params}) do
    changeset = conn.assigns.current_user
    |>build_assoc(:posts)
    |>Post.changeset(post_params)
end

#3.2 Get's user's posts through assoc function 
def index(conn, _params) do
    posts = Repo.all(assoc(conn.assigns.current_user))
end