find_or_create上有很多直通关系 [英] find_or_create on a has many through relationship

问题描述

我的应用中有很多直通关系:

I have a has many through relationship in my app:

演出通过=> 阵容

频段按:name

class Show < ActiveRecord::Base
attr_accessible :city_id, :title, :dateonly, :timeonly, :image, :canceled, :venue_attributes, :bands_attributes

  belongs_to :city
  belongs_to :venue
  has_many :lineups
  has_many :bands, through: :lineups
  has_and_belongs_to_many :users
end


class Lineup < ActiveRecord::Base
  belongs_to :show
  belongs_to :band


end


class Band < ActiveRecord::Base
  attr_accessible :name, :website, :country, :state
  has_many :lineups
  has_many :shows, through: :lineups

  validates :name, presence: true
  validates_uniqueness_of :name
  before_save :titleize_name

  private
    def titleize_name
      self.name = self.name.titleize
    end

end

新乐队的创建是这样的:

New Bands are created like this:

(假设我们已经保存了一个名为s1的放映记录)

(lets say we have a show record already saved called s1)

> s1.bands.new(name: "Wet Food")
> s1.save

现在，只有在不存在名为"Wet Food"的乐队时，此功能才会保存

Right now this will only save if a band named "Wet Food" doesn't already exist

在哪种模型中以这种关系进行Band.find_or_create的最佳位置，以便在存在相同名称的情况下可以使用现有的乐队?

In which model is the best place to do a Band.find_or_create in this relationship so that an existing band can be used if one with the same name exists?

推荐答案

这通常是在Controller(或者可能是服务对象)中进行的调用类型，而不是在Model中进行的调用类型.这实际上取决于您要在应用程序中尝试完成的特定用户流.基本上，只要您已经在使用s1.bands.new的地方，都可以使用它:

This is generally the type of call that would go in a Controller (or maybe a service object), but not in a Model. It really depends on the particular user flow that you're trying to accomplish in your app. Basically, where ever you are already using s1.bands.new, you could use this instead :

s1.bands.where(name: 'Wet Food').first_or_create

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