ruby-on-rails - 保存事件记录，关联对象以什么顺序保存？

Question

在 rails 中，当保存一个 active_record 对象时，它的关联对象也会被保存。但是 has_one 和 has_many 关联在保存对象时有不同的顺序。

我有三个简化模型:

class Team < ActiveRecord::Base
  has_many :players
  has_one :coach
end

class Player < ActiveRecord::Base
  belongs_to :team
  validates_presence_of :team_id
end

class Coach < ActiveRecord::Base
  belongs_to :team
  validates_presence_of :team_id
end

我预计当 team.save被称为，球队应该在其相关的教练和球员之前被拯救。

我使用以下代码来测试这些模型:

t = Team.new
team.coach = Coach.new
team.save!

team.save!返回真。

但在另一个测试中:

t = Team.new
team.players << Player.new
team.save!

team.save!给出以下错误:

> ActiveRecord::RecordInvalid:
> Validation failed: Players is invalid

我发现 team.save!按以下顺序保存对象:1) 球员、2) 团队和 3) 教练。这就是我收到错误的原因:当玩家被保存时，团队还没有 ID，所以 validates_presence_of :team_id播放器失败。

有人可以向我解释为什么按此顺序保存对象吗？这对我来说似乎不合逻辑。

Answer 1

您应该使用“validates_related”来完成

检查 Here

就像没有检查一样

class Team < ActiveRecord::Base
  has_many :players
  has_one :coach
  validates_associated :players, :coach  ###MOST IMPORTANT LINE 
end

class Player < ActiveRecord::Base
  belongs_to :team
  validates_presence_of :team_id
end

class Coach < ActiveRecord::Base
  belongs_to :team
  validates_presence_of :team_id
end

在您的 Controller 中

t = Team.new

@coach = t.build_coach(:column1=> "value1", :column2=> "value2" )  # This create new object with @coach.team_id= t.id
@players = t.players.build

t.save#This will be true it passes the validation for all i.e. Team, COach & Player also save all at once otherwise none of them will get saved.