How to stop create if a parameter value is empty/missing? - ruby-on-rails

Question

I'm trying to create an event with some nested params, but I want to return a 400 if certain parameters are empty. Is there some built in way to do this without checking params and returning early?
for exmaple:
event = Event.create! params.require(:event).permit(
:name,
:owner_id,
attachments: [],
location_attributes: [
:custom,
:building,
:street_1,
:street_2,
:city,
:state,
:postal,
:country,
:latitude,
:longitude,
],
)
Let's say I want to reject if latitude and longitude are empty - what's the best way to do that?

Answer 1

You can use require on your desired attributes too, but it's a bit tricky. Check the last example here https://edgeapi.rubyonrails.org/classes/ActionController/Parameters.html#method-i-require
In your case it would be something like:
params.require(:event).permit(
:name,
:owner_id,
attachments: [],
location_attributes: [
:custom,
:building,
:street_1,
:street_2,
:city,
:state,
:postal,
:country,
:latitude,
:longitude,
],
).tap do |event_params|
event_params[:location_attributes].require(:latitude, :longitude)
end
I'm not sure if that's the final syntax since the doc example does not have nested attributes, but I hope it points you in the right direction.

Answer 2

While you can just call require several times:
def event_params
params.require(:event).require(:location_attributes).tap do |p|
p.require(:latitude)
p.require(:longitude)
end
# ...
params.require(:event).permit(
:name,
:owner_id,
attachments: [],
location_attributes: [
:custom,
:building,
:street_1,
:street_2,
:city,
:state,
:postal,
:country,
:latitude,
:longitude,
]
)
end
This really bloats your controller.
And I think you are really just overcomplicating something that should be handled by using the non-bang persistence methods (the ones that don't raise an error and that don't end with !) and validations on the model layer. Exceptions should not be used for the normal controller flow.
The bang methods such as create! should only really be used in a non-interactive context (such as seed files) or when you are using a transaction and need to rollback the transaction on failure.
So you use can use .require to bail early if the params are completely unusable but for the more "normal" case where a one the attributes is missing or blank should be handled by validations.
This lets you actually provide feedback to the user/client about what is missing and the 422 response is actually more appropriate.
def create
#event.new(event_params)
if #event.save
respond_to do |f|
f.html { redirect_to #event }
f.json { status :created, location: #event }
end
else
respond_to do |f|
f.html { render :new}
f.json { status :unprocessable_entity }
end
end
end
class Event < ApplicationRecord
has_many :locations
accepts_nested_attributes_for :locations
validates_associated :locations
end
class Location < ApplicationRecord
belongs_to :event
validates_presence_of :latitude, :longitude
end