ruby-on-rails - 如何防止连接表中出现重复记录

Question

我对 Ruby 和 Rails 还很陌生，所以请耐心等待。

我有两个模型 Player，并且 Reward 通过 has_many 通过关系加入，如下所示。我的玩家模型有一个属性点。当玩家积累积分时，他们会获得奖励。我想要做的是在 Player 模型上放置一个方法，该方法将在更新之前运行，并为他们拥有的积分提供适当的奖励，如下所示。

但是我想这样做，如果玩家已经获得奖励，则不会重复奖励，也不会导致错误。

class Player < ActiveRecord::Base
  has_many :earned_rewards, -> { extending FirstOrBuild }
  has_many :rewards, :through => :earned_rewards

  before_update :assign_rewards, :if => :points_changed?

  def assign_rewards
    case self.points
    when 1000
      self.rewards << Reward.find_by(:name => "Bronze")
    when 2000
      self.rewards << Reward.find_by(:name => "Silver")
    end
end

class Reward < ActiveRecord::Base
  has_many :earned_rewards
  has_many :players, :through => :earned_rewards
end

class EarnedReward < ActiveRecord::Base
  belongs_to :player
  belongs_to :reward

  validates_uniqueness_of :reward_id, :scope => [:reward_id, :player_id]
end

module FirstOrBuild
  def first_or_build(attributes = nil, options = {}, &block)
    first || scoping{ proxy_association.build(attributes, &block) }
  end
end

Answer 1

您还应该在数据库中验证它

在迁移文件中添加以下内容-

add_index :earnedrewards, [:reward_id, :player_id], unique: true