我有一个has_many_through关联，其中User有许多Project到ProjectUser.Rails有一些神奇的功能，可以通过以下方式更新这种关系:
u = User.first
u.update(project_ids: [...])
有没有一种干净利落的方法来用create做同样的事情？
运行User.create(name: ..., project_ids: [...])失败，返回Validation failed: Project users is invalid.
我怀疑这是因为Rails试图在创建User记录之前创建ProjectUser记录，并且在连接表上有一些内置的验证，以验证连接的两端是否已经存在.ProjectUser型号没有定制验证.
class ProjectUser < ApplicationRecord
belongs_to :project
belongs_to :user
end
有什么简单的方法可以绕过这个问题吗？
Active Record supports automatic identification for most associations with standard names. However, Active Record will not automatically identify bi-directional associations that contain the :through or :foreign_key options.(可以勾选here)
所以你必须明确地定义inverse_of.
class Project < ApplicationRecord
has_many :project_users, foreign_key: :project_id, inverse_of: :project
has_many :users, through: :project_users
end
class User < ApplicationRecord
has_many :project_users, foreign_key: :user_id, inverse_of: :user
has_many :projects, through: :project_users
end
class ProjectUser < ApplicationRecord
belongs_to :project
belongs_to :user
end