Rails PG::ForeignKeyViolation: ERROR: insert or update on table - ruby-on-rails

Question

I've got two models with simple belongs_to has_many relation, as follows:
class Property < ApplicationRecord
belongs_to :portfolio, optional: true
end
class Portfolio < ApplicationRecord
has_many :properties, dependent: :nullify
end
Which were created by migrations:
class CreateProperties < ActiveRecord::Migration[6.0]
def change
create_table :properties do |t|
t.string :name, null: false
t.string :status, null: false
t.references :portfolio, foreign_key: true
t.timestamps
end
end
end
class CreatePortfolios < ActiveRecord::Migration[6.0]
def change
create_table :portfolios do |t|
t.string :name, null: false
t.timestamps
end
end
end
When I want to create new Property with portfolio_id: 1 which doesn't exist I'm getting an error:
PG::ForeignKeyViolation: ERROR: insert or update on table "properties" violates foreign key constraint "fk_rails_760fb8258a" DETAIL: Key (portfolio_id)=(1) is not present in table "portfolios".
How to handle such error and display to user information such as "portfolio_id doesn't exist" ?
Create action is pretty standard:
property_controller.rb
def create
#property = Property.new(property_params)
respond_to do |format|
if #property.save
format.html { redirect_to #property, notice: 'Property was successfully created.' }
format.json { render :show, status: :created, location: #property }
else
format.html { render :new, status: :unprocessable_entity }
format.json { render json: #property.errors, status: :unprocessable_entity }
end
end
end

Answer 1

The error makes sense, since you're trying to create a property with a portfolio_id that doesn't exist. Since you added the optional: true to belongs_to :portfolio in the Property class, you removed the validation that normally comes with the belongs_to.
The best way of avoiding that would be to display a dropwdown in the form for a new portfolio that contains all the possible properties. That would also be better in terms of UX because the user would not have to remember the id of a property.