Example with TODO app.
The migration to add the index
class AddIndexOnTitleAndUserToTodocards < ActiveRecord::Migration
def change
add_index :todocards, [:title, :user_id], unique: true
end
end
The result in the databse schema
add_index "todocards", ["title", "user_id"], name: "index_todocards_on_title_and_user_id", unique: true
The model, doesn’t need the validation on uniqueness, only needs the presence validation
class Todocard < ActiveRecord::Base
# now done in database level -> validates :title, presence: true, uniqueness: { scope: :user }
validates :user_id, :title, presence: true
belongs_to :user
end
The controller, needs to be added the rescue_from clause
def update
begin
respond_to do |format|
if @todocard.update(todocard_params)
format.html { redirect_to @todocard, notice: 'Todocard was successfully updated.' }
format.json { render :show, status: :ok, location: @todocard }
else
format.html { render :edit }
format.json { render json: @todocard.errors, status: :unprocessable_entity }
end
end
rescue ActiveRecord::RecordNotUnique
# validation at DB level
@todocard.errors["title"] = "Title must be present and unique"
respond_to do |format|
format.html { render :edit }
format.json { render json: @todocard.errors, status: :unprocessable_entity }
end
end
end
def create
begin
@todocard = Todocard.new(todocard_params)
respond_to do |format|
if @todocard.save
format.html { redirect_to @todocard, notice: 'Todocard was successfully created.' }
format.json { render :show, status: :created, location: @todocard }
else
format.html { render :new }
format.json { render json: @todocard.errors, status: :unprocessable_entity }
end
end
rescue ActiveRecord::RecordNotUnique
# validation at DB level
@todocard.errors["title"] = "Title must be present and unique"
respond_to do |format|
format.html { render :new }
format.json { render json: @todocard.errors, status: :unprocessable_entity }
end
end
end