Rails - 是否有可能找到违反唯一验证的记录

Question

Considering following as an example

class SuperHero < ActiveRecord::Base
  validates :weapon, uniqueness: true
end

So when I create

SuperHero.create!(name: "Thor", weapon: "hammer")
SuperHero.create!(name: "Spiderman", weapon: "hammer") => Weapon has already been taken

Is it possible to add, the error message Weapon has already been taken by Thor using the default unique validation? So that the user can easily find the whom currently the weapon is assigned to?

Answer 1

You will need to implement your own validation. Something like this:

class SuperHero < ActiveRecord::Base
  validates :weapon, uniqueness: true

  before_validation -> {
    existing_super_hero = SuperHero.find_by_weapon self.weapon

    if existing_super_hero && existing_super_hero.id != self.id
      self.errors.add(:base, "Weapon has already been taken by #{existing_super_hero.name}")
      throw :abort
    end
  }
end