已解决请在问题末尾和我下面的回答中阅读更多内容。
已接受的问题解决了主要错误。
我自己的回答给出了如何解决的细节说明。
原始问题:
我正在尝试建立多对多关系。我已经阅读了很多关于堆栈交换以及 Rails 手册和教程的文章。直到今天我还以为我已经知道该怎么做,但现在我需要检索整个模型链的信息,但数据库中没有任何结果。
关系是用户 <-> 成员资格 <-> 用户组 <-> 访问权限 <-> 函数,成员资格和访问权限为“直通”模型。
class User < ActiveRecord::Base
has_many :memberships
has_many :usergroups, :through => :memberships
has_many :functions, :through => :usergroups
end
class Membership < ActiveRecord::Base
belongs_to :user
belongs_to :usergroup
end
class Usergroup < ActiveRecord::Base
has_many :accessrights
has_many :functions, :through => :accessrights
has_many :memberships
has_many :users, :through => :memberships
end
class Accessright < ActiveRecord::Base
belongs_to :function
belongs_to :usergroup
end
class Function < ActiveRecord::Base
has_many :accessrights
has_many :usergroups, :through => :accessrights
end
我掌握了一个用户对象,我想在列表中获取该用户对象的函数名称。我在辅助模块中尝试这样做:
# Loads the functions the current user via her usergroup has access right to (if any).
def load_user_functions
if @current_user_functions.nil?
@current_user_functions = []
if logged_in?
@current_user.functions.each do |f|
@current_user_functions << f.name
end
end
end
end
通过阅读手册,我得到的印象是,如果我正确设置了模型,我可能会隐式地执行类似 @current_user.functions.each 的操作。
我在网站上放了一个调试器。我在登录后显示当前用户,但没有功能信息。登录后它们保持为空:
# Logs in the given user.
def log_in(user)
session[:user_id] = user.id
# reset function access rights
@current_user_functions = nil
load_user_functions
end
# Returns the current logged-in user (if any).
def current_user
@current_user ||= User.find_by(id: session[:user_id])
end
# Returns true if the user is logged in, false otherwise.
def logged_in?
!current_user.nil?
end
这里是表的数据库架构,由我的迁移创建:
create_table "accessrights", id: false, force: true do |t|
t.integer "usergroup_id"
t.integer "function_id"
t.datetime "created_at"
t.datetime "updated_at"
end
add_index "accessrights", ["usergroup_id", "function_id"], name: "index_accessrights_on_function_id_and_usergroup_id", unique: true, using: :btree
create_table "functions", force: true do |t|
t.string "name"
t.datetime "created_at"
t.datetime "updated_at"
end
create_table "memberships", id: false, force: true do |t|
t.integer "user_id"
t.integer "usergroup_id"
t.datetime "created_at"
t.datetime "updated_at"
end
add_index "memberships", ["user_id", "usergroup_id"], name: "index_memberships_on_user_id_and_usergroup_id", unique: true, using: :btree
create_table "usergroups", force: true do |t|
t.string "name"
t.datetime "created_at"
t.datetime "updated_at"
end
create_table "users", force: true do |t|
t.string "username"
t.string "email"
t.datetime "created_at"
t.datetime "updated_at"
t.string "password_digest"
end
这是调试器,我用它来检查变量的内容。也许调试器无法处理这样的列表?
<%= debug(@current_user) if Rails.env.development? %>
<%= debug(@current_user_functions) if Rails.env.development? %>
如果它有意义,第二个调试器会显示:
---
...
我的数据库种子的摘录:
@function3 = Function.create!(name: "ViewCreateEditDeleteUsers")
@usergroup3 = Usergroup.create!(name: "Admin") # gets right to view, create, edit and delete user groups and users
Accessright.create!(function_id: @function3.id,
usergroup_id: @usergroup3.id)
@user =
User.create!(username: "AOphagen",
email: "ophagen@test.de",
password: "testing", password_confirmation: "testing", )
Membership.create!(user_id: @user.id,
usergroup_id: @usergroup3.id)
在 BroiSatse 的有用建议之后,我尝试了 Rails 控制台(哎哟,应该是我最喜欢的工具),结果是,我已经正确设置了数据库:
User.find_by(username:"AOphagen").functions.first.name
User Load (0.9ms) SELECT "users".* FROM "users" WHERE "users"."username" = 'AOphagen' LIMIT 1
Function Load (2.1ms) SELECT "functions".* FROM "functions" INNER JOIN "accessrights" ON "functions"."id" = "accessrights"."function_id" INNER JOIN "usergroups" ON "accessrights"."usergroup_id" = "usergroups"."id" INNER JOIN "memberships" ON "usergroups"."id" = "memberships"."usergroup_id" WHERE "memberships"."user_id" = $1 ORDER BY "functions"."id" ASC LIMIT 1 [["user_id", 1]]
=> "ViewCreateEditDeleteUsers"
已解决 主要错误在数据库设置中。这已通过我选择的解决问题的答案解决(再次感谢!)。答案简洁、正确且有帮助。
问题的细节需要更多的时间来解决,所以我在下面给出了详细的答案。
我很想知道为什么我最初的想法(我知道它不是 Ruby-like)行不通 - 以及为什么 lazy fetch 现在行得通了,拜托!
最佳答案
对于要调用用户的每个方法,您都必须创建一个方法。在这种情况下,您应该像这样使用嵌套的 has_many :through
:
class User < ActiveRecord::Base
has_many :memberships
has_many :usergroups, through: :memberships
has_many :functions, through: :usergroups
end
关于ruby-on-rails - 如何设置多层 Rails ActiveRecord 多对多关系?,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/28561727/