范围的反轨

Question

是否有否定范围结果的方法？我有3个模型，由has_many关联：通过关联

user.rb

class User < ActiveRecord::Base
    has_many :user_training_maps
    has_many :trainings, through: :user_training_maps
end

training.rb

class Training < ActiveRecord::Base
    has_many :user_training_maps
    has_many :users, through: :user_training_maps
end

user_training_map.rb

class UserTrainingMap < ActiveRecord::Base
    belongs_to :user
    belongs_to :training
end

在此之前，我想查找所有属于（已注册）培训的用户。在user.rb中，这有效：

scope :all_enrolled, -> { joins(:trainings) }

现在，我需要帮助来查找不属于（未注册）培训的所有用户。我无法scope :all_unenrolled, -> { !joins(:trainings) } 使它起作用： 相反，它只是返回所有用户。就像是unenrolled users = (all users) - (enrolled users)

Answer 1

尝试这个

scope : all_enrolled, -> { joins(:trainings) } scope :not_enrolled, -> { where.not(id: all_enrolled) }