How can I get my rails controller (CREATE) to accept/POST multiples JSON records? - ruby-on-rails

Question

I have a backend Rails JSON API. Right now, I am only able to create one record per POST based on the way I've coded my controller.
Let's say we have an application where Users can create To-Do Lists and in those lists they can create items.
3 models for our example, User, UserList, and UserListItems
User has_many UserLists
UserLists has_many UserListItems
Now right now, I'm updating UserListItems with a POST, but I can only add one item at a time. The JSON looks like...
{
"user_list_item":
{
"item_title": "Buy Milk"
}
}
And using Active Model Serializers, I am returning the record that it creates, and it looks as follows...
respond_with :api, :v1, #current_user, user_list, user_list_item, location: nil, serializer: Api::V1::UserListItemSerializer
{
"user_list_item": {
"id": 11,
"user_list_id": 2,
"item_title": "Buy Milk"
}
}
There is a serious flaw with this. If a User creates a 'Grocery To-Do List' and we POST 1 UserList record... that's fine. But then they might begin to fill the grocery list and add 3 things at once. "Buy Milk", "Buy Eggs", "Get Gas". We now need to POST to UserItemList 3 times, and that's far from ideal. What if they added 20 items. We should aim to add all 20 in 1 POST.
How can I do this?!?
1) Can someone show me the entire sample code for the CREATE in the controller to do this, as I learn best by seeing/doing syntax. I want to be able to pass in...
{
"user_list_item":
[
{
"item_title": "Buy Milk"
},
{
"item_title": "Buy Eggs"
},
{
"item_title": "Get Gas"
}
]
}
and have my controller parse, loop, and create them. 2) And I also want to be able to return the record(s) to the creator via Active Model Serializers. So for example, all 3 of these newly added records in one return (mostly I'm just interested in the first thing right now though).
EDIT: Adding my original controller#create code
if authenticate_user
user_list = #current_user.user_lists.find_by_id(params[:user_list_id])
user_list_item = user_list.user_list_items.new(user_list_item_params)
if (user_list_item.save!)
respond_with :api, :v1, #current_user, user_list, user_list_item, location: nil, serializer: Api::V1::UserListItemSerializer
else
render json: { error: "Could not create new User List Item."}, status: :unprocessable_entity
end
else
render json: { error: "User is not signed in." }, status: :unauthorized
end
private
def user_list_item_params
params.require(:user_list_item).permit(:user_list_id, :title, :due_date)
end
Now, with #Arvoreniad's suggestion below, I now have the following...
if authenticate_user
#user_list = #current_user.user_lists.find_by_id(params[:user_list_id])
#error = false
user_list_item_params[:user_list_item].each do |attribute|
item = #user_list.user_list_items.new
item.title = attribute.title
item.due_date = attribute.due_date
#error = true unless item.save
end
if (error)
????????????????
else
render json: { error: "Could not create new User List Item(s)."}, status: :unprocessable_entity
end
private
def user_list_item_params
params.require(:user_list_item).permit(:user_list_id, :title, :due_date)
end
My new questions are
1) Where all the ?'s are... where I was previously using ActiveModelSerializers to show the newly added record, how can I return something showing all the newly added records? Or this that not typical of an API? Is it just common to return something empty and just go off of whether it was successful or not?
2) Can-I/Should-I create both things in 1 POST (UserList and Multiple UserListItem's all in 1 POST)? If so, how?
3) How can I rollback all saves if one does not work. Let's say I'm trying to add 10 items, and 9 succeed but 1 fails, how do I roll them all back?

Answer 1

Your question is a little difficult to answer without your previous controller code, but this should give you a starting point based on the info you supplied. EDIT: Added the code for points 1 and 3.
If you want to create a UserList in the same action, just post the required data and create one from the parameters, rather than finding it in the database. I can help you with this if you'd like, but it shouldn't be too hard.
def create
#user_list = UserList.find(params[:id)
#error = false # Use this to check before rendering if there has been an error.
params[:user_list_item].each do |attributes|
item = UserListItem.new
item.item_title = attributes.item_title
item.user_list_id = #user_list.id
#error = true unless item.valid?
#items << item
end
if(#error)
render json: { error: "Could not create new User List Item(s)."}, status: :unprocessable_entity
else
#items.each do |item|
item.save
end
serialized = ActiveModel::ArraySerializer.new(#items, each_serializer: UserListItemSerializer)
render json: serialized
end
end