Rails store to different tables within the same controller - ruby-on-rails

Question

I have two models, Livestock and History
a livestock has many histories and history belongs to livestock
This is the create method inside the LivestockController
# POST /livestocks
# POST /livestocks.json
def create
#livestock = Livestock.new(livestock_params.permit!)
respond_to do |format|
if #livestock.save
format.html { redirect_to #livestock }
flash[:success] = "Livestock was successfully created"
format.json { render :show, status: :created, location: #livestock }
else
format.html { render :new }
format.json { render json: #livestock.errors, status: :unprocessable_entity }
end
end
end
I wanted to create a record in the histories table with
history = History.new(livestock_id: #livestock.id, event: "Purchased", event_date: #livestock.purchase_date, image: #livestock.image)
history.save!
inside the create method
How can I do it? I can't put it in the create method because it says
Validation failed: Livestock must exist
apparently #livestock has not yet have the id attribute
Edit:
it still raises the same exception when I put it after
if #livestock.save
However I found a work around by using the session variable. Since it is redirected to the show page, I created the following inside the create method
session[:created] = "created"
And in my show method
# GET /livestocks/1
# GET /livestocks/1.json
def show
if session[:created] == "created"
history = History.new(livestock_id: params[:id], event: "Purchased", event_date: #livestock.purchase_date, image: #livestock.image)
history.save!
session.delete(:created)
end
end
Now I am wondering what are consequences if I use this approach.

Answer 1

Livestock record is created when you call save (and there is no validation error). So one option is to create the history inside this if condition:
if #livestock.save
Another option is to use after_create callback in the livestock model that will create a history object right after creating livestock. You have to be careful because the callback might be called when you do not need it (i.e. when importing data).
The last option is to create a separate service object that will create livestock and all other required objects. That's probably the best approach, but it will require more customized code.
Update
Please also make sure to move if/else block outside the respond_to block:
if #livestock.save
# create history object here
respond_to do |format|
format.html { redirect_to #livestock }
flash[:success] = "Livestock was successfully created"
format.json { render :show, status: :created, location: #livestock}
end
else
respond_to do |format|
format.html { render :new }
format.json { render json: #livestock.errors, status: :unprocessable_entity }
end
end