如何创建has_many：通过关联并设置联接模型属性

Question

我有这些模特

class Release < ActiveRecord::Base
  has_many :recordings, through: :release_recordings
  has_many :release_recordings, inverse_of: :release
end

class Recording < ActiveRecord::Base
  has_many :releases, through: :release_recordings
  has_many :release_recordings, inverse_of: :recording

  accepts_nested_attributes_for :release_recordings
end

class ReleaseRecording < ActiveRecord::Base
  belongs_to :release
  belongs_to :recording
end

我想以这种方式创建记录，将position条目添加到联接表中：

release.recordings.create!(name: name, release_recordings_attributes: { 0 => {position: position} })

问题在于，这最终试图在release_recordings表中创建两个记录。 一种是release_id为NULL ，另一种是position NULL 。 当然，我只想创建一个没有任何NULL字段的记录。

我最终做了这个（它按预期工作）：

recording = release.recordings.create!(name: name)
recording.release_recordings.find_by_release_id(release).update_attributes!(position: position)

...但是当我应该已经引用了它时，查询我刚刚创建的记录似乎很愚蠢。

在为发行版本创建新的记录记录的同时，如何设置位置字段？

Answer 1

release.recordings.create!(name: name).release_recordings.create(position: position)

不确定这是否行得通..

class Recording < ActiveRecord::Base
  has_many :releases, through: :release_recordings
  has_many :release_recordings, inverse_of: :recording

  accepts_nested_attributes_for :release_recordings, reject_if: lambda { |release_recording| release_recording['release_id'].blank? }
end