让我们尝试对您的问题进行一些重构,并用关联替换has_and_belongs_to_many
关联has_many, through
,我们将在模型上添加另一个has_many, through
关联,Character
如下所示:
class Membership < ActiveRecord::Base
belongs_to :user
belongs_to :group
end
class Group < ActiveRecord::Base
has_many :memberships
has_many :users, through: :memberships
end
class User < ActiveRecord::Base
has_many :memberships
has_many :groups, through: :memberships
has_many :characters
end
class Character < ActiveRecord::Base
belongs_to :user
has_many :groups, through: :user
end
模型是 a和 aMembership
之间关系的表示-本质上是使用时隐藏的连接表。我更喜欢看到这种关系(特别是如果它很重要)。User
Group
has_and_belongs_to_many
我们还在Character
模型上Group
与与用户关联的 s 建立了关联。当我们尝试加入我们的范围时,这很有帮助。
充实Character
模型,让我们添加以下内容:
sifter :by_user do |user|
user_id == user.id
end
sifter :public do
public
end
使用筛选器作为我们的构建块,我们可以添加以下内容以获取可见字符(如您定义的那样):
def self.get_visible(user)
Character.uniq.joins{groups.outer}.where{(sift :public)|(sift :by_user, user)|(groups.id.in(user.groups))}
end
此方法接受一个实例User
并找到以下Character
s:
- 所有公共角色。
- 用户的所有角色。
- 属于用户组的所有字符。
然后我们只从这些集合中获取不同的字符列表。
从 Rails 控制台:
irb(main):053:0> Character.get_visible(User.find(4))
User Load (0.6ms) SELECT "users".* FROM "users" WHERE "users"."id" = $1 LIMIT 1 [["id", 4]]
Group Load (0.7ms) SELECT "groups".* FROM "groups" INNER JOIN "memberships" ON "groups"."id" = "memberships"."group_id" WHERE "memberships"."user_id" = 4
Character Load (0.9ms) SELECT DISTINCT "characters".* FROM "characters" LEFT OUTER JOIN "users" ON "users"."id" = "characters"."user_id" LEFT OUTER JOIN "memberships" ON "memberships"."user_id" = "users"."id" LEFT OUTER JOIN "groups" ON "groups"."id" = "memberships"."group_id" WHERE ((("characters"."public" OR "characters"."user_id" = 4) OR "groups"."id" IN (2)))
[
[0] #<Character:0x00000005a16b48> {
:id => 4,
:user_id => 4,
:name => "Testiculies",
:created_at => Tue, 13 Aug 2013 14:35:50 UTC +00:00,
:updated_at => Tue, 13 Aug 2013 14:35:50 UTC +00:00,
:public => nil
},
[1] #<Character:0x00000005d9db40> {
:id => 1,
:user_id => 1,
:name => "conan",
:created_at => Mon, 12 Aug 2013 20:18:52 UTC +00:00,
:updated_at => Tue, 13 Aug 2013 12:53:42 UTC +00:00,
:public => true
}
]
要查找特定字符的所有字符User
,请向模型添加实例方法User
:
def get_visible_characters
Character.get_visible(self)
end
我认为这会让你到达你想去的地方。