我有一个非常标准的设计用户模型模式，其中包含角色和userRoles的多对多模型:
#teacher or student
create_table "roles", :force => true do |t|
t.string "name"
end
create_table "user_roles", :force => true do |t|
t.integer "user_id"
t.integer "role_id"
end
add_index "user_roles", ["role_id"], :name => "index_user_roles_on_role_id"
add_index "user_roles", ["user_id"], :name => "index_user_roles_on_user_id"
create_table "users", :force => true do |t|
t.string "email", :default => "", :null => false
t.string "encrypted_password", :default => "", :null => false
........more stuff....
end
add_index "users", ["email"], :name => "index_users_on_email", :unique => true
add_index "users", ["reset_password_token"], :name => "index_users_on_reset_password_token", :unique => true
end
角色是老师和学生。我想创建一个具有多对多学生(具有学生角色的用户)和多对多教师(具有教师角色的用户)的Clazz(如在学校课堂中)模型。
我想它应该是这样的，但是我不太明白:
rails g scaffold Clazz name:string time:datetime has_many:users(of type student) has_many:users(of type teacher)我怎么做最后两个?我是否首先通过关联迁移(teacherClass和studentClass)创建has_many ?还是有辅助方法?
也许我只是找不到合适的教程或例子，所以我也可以使用其中一个…提前感谢
这是关于我尝试@Cody Caughlan的答案的更多信息
模式。rb:
ActiveRecord::Schema.define(:version => 20130523111519) do
create_table "class_instructions", :force => true do |t|
t.string "name"
t.datetime "time"
t.integer "user_id"
t.datetime "created_at", :null => false
t.datetime "updated_at", :null => false
end
add_index "class_instructions", ["user_id"], :name => "index_class_instructions_on_user_id"
create_table "roles", :force => true do |t|
t.string "name"
t.datetime "created_at", :null => false
t.datetime "updated_at", :null => false
end
create_table "songs", :force => true do |t|
t.string "title"
t.string "content"
t.datetime "created_at", :null => false
t.datetime "updated_at", :null => false
t.integer "user_id"
t.string "fractionRepresentation"
t.string "measureRepresentation"
end
create_table "user_roles", :force => true do |t|
t.integer "user_id"
t.integer "role_id"
t.datetime "created_at", :null => false
t.datetime "updated_at", :null => false
end
add_index "user_roles", ["role_id"], :name => "index_user_roles_on_role_id"
add_index "user_roles", ["user_id"], :name => "index_user_roles_on_user_id"
create_table "users", :force => true do |t|
t.string "email", :default => "", :null => false
t.string "encrypted_password", :default => "", :null => false
t.string "reset_password_token"
t.datetime "reset_password_sent_at"
t.datetime "remember_created_at"
t.integer "sign_in_count", :default => 0
t.datetime "current_sign_in_at"
t.datetime "last_sign_in_at"
t.string "current_sign_in_ip"
t.string "last_sign_in_ip"
end
add_index "users", ["email"], :name => "index_users_on_email", :unique => true
add_index "users", ["reset_password_token"], :name => "index_users_on_reset_password_token", :unique => true
end
用户。Rb模型:
class User < ActiveRecord::Base
#DEVISE STUFF
#== Associations
has_many :user_roles, :dependent => :destroy
has_many :roles, :through => :user_roles
has_many :songs
#== Instance Methods
def thisUsersID
self.id
end
def student_classes(class_instruction_name)
member_classes(class_instruction_name, 'Student')
end
def teacher_classes(class_instruction_name)
member_classes(class_instruction_name, Role::TEACHER)
end
private
def member_classes(class_instruction_name, type)
ClassInstruction
.joins(:user_role)
.where(["user_role.user_id = ?", id])
.joins("INNER JOIN roles ON roles.id = user_roles.role_id")
.where("roles.name = ?", type)
.where("class_instruction.name = ?", class_instruction_name)
end
end
user_role。rb模型:
class UserRole < ActiveRecord::Base
belongs_to :user
belongs_to :role
has_many :class_instructions, :dependent => :destroy
end
角色。rb模型
class Role < ActiveRecord::Base
has_many :user_roles, :dependent => :destroy
end
class_instruction。Rb模型(名称为'ss'和'math-101')
class ClassInstruction < ActiveRecord::Base
belongs_to :user_role
end
Loading development environment (Rails 3.2.2)
1.9.3-p429 :001 > U = User.find(3)
User Load (3.2ms) SELECT "users".* FROM "users" WHERE "users"."id" = ? LIMIT 1 [["id", 3]]
=> #<User id: 3, email: "stu@test.org", encrypted_password: "$2a$10$2DxWWV34BRFJoLboYyWCIeXEtCPYOSe8JqpTmFU6W2i1...", reset_password_token: nil, reset_password_sent_at: nil, remember_created_at: nil, sign_in_count: 0, current_sign_in_at: nil, last_sign_in_at: nil, current_sign_in_ip: nil, last_sign_in_ip: nil>
1.9.3-p429 :002 > U.student_classes('math-101').all
ClassInstruction Load (0.2ms) SELECT "class_instructions".* FROM "class_instructions" INNER JOIN "user_roles" ON "user_roles"."id" = "class_instructions"."user_role_id" INNER JOIN roles ON roles.id = user_roles.role_id WHERE (user_role.user_id = 3) AND (roles.name = 'Student') AND (class_instruction.name = 'math-101')
SQLite3::SQLException: no such column: user_role.user_id: SELECT "class_instructions".* FROM "class_instructions" INNER JOIN "user_roles" ON "user_roles"."id" = "class_instructions"."user_role_id" INNER JOIN roles ON roles.id = user_roles.role_id WHERE (user_role.user_id = 3) AND (roles.name = 'Student') AND (class_instruction.name = 'math-101')
ActiveRecord::StatementInvalid: SQLite3::SQLException: no such column: user_role.user_id: SELECT "class_instructions".* FROM "class_instructions" INNER JOIN "user_roles" ON "user_roles"."id" = "class_instructions"."user_role_id" INNER JOIN roles ON roles.id = user_roles.role_id WHERE (user_role.user_id = 3) AND (roles.name = 'Student') AND (class_instruction.name = 'math-101')
from /Users/phycom06/.rvm/gems/ruby-1.9.3-p429/gems/sqlite3-1.3.7/lib/sqlite3/database.rb:91:in `initialize'
from /Users/phycom06/.rvm/gems/ruby-1.9.3-p429/gems/sqlite3-1.3.7/lib/sqlite3/database.rb:91:in `new'
from /Users/phycom06/.rvm/gems/ruby-1.9.3-p429/gems/sqlite3-1.3.7/lib/sqlite3/database.rb:91:in `prepare'
from /Users/phycom06/.rvm/gems/ruby-1.9.3-p429/gems/activerecord-3.2.2/lib/active_record/connection_adapters/sqlite_adapter.rb:246:in `block in exec_query'
from /Users/phycom06/.rvm/gems/ruby-1.9.3-p429/gems/activerecord-3.2.2/lib/active_record/connection_adapters/abstract_adapter.rb:280:in `block in log'
from /Users/phycom06/.rvm/gems/ruby-1.9.3-p429/gems/activesupport-3.2.2/lib/active_support/notifications/instrumenter.rb:20:in `instrument'
from /Users/phycom06/.rvm/gems/ruby-1.9.3-p429/gems/activerecord-3.2.2/lib/active_record/connection_adapters/abstract_adapter.rb:275:in `log'
from /Users/phycom06/.rvm/gems/ruby-1.9.3-p429/gems/activerecord-3.2.2/lib/active_record/connection_adapters/sqlite_adapter.rb:242:in `exec_query'
from /Users/phycom06/.rvm/gems/ruby-1.9.3-p429/gems/activerecord-3.2.2/lib/active_record/connection_adapters/sqlite_adapter.rb:460:in `select'
from /Users/phycom06/.rvm/gems/ruby-1.9.3-p429/gems/activerecord-3.2.2/lib/active_record/connection_adapters/abstract/database_statements.rb:18:in `select_all'
from /Users/phycom06/.rvm/gems/ruby-1.9.3-p429/gems/activerecord-3.2.2/lib/active_record/connection_adapters/abstract/query_cache.rb:63:in `select_all'
from /Users/phycom06/.rvm/gems/ruby-1.9.3-p429/gems/activerecord-3.2.2/lib/active_record/querying.rb:38:in `block in find_by_sql'
from /Users/phycom06/.rvm/gems/ruby-1.9.3-p429/gems/activerecord-3.2.2/lib/active_record/explain.rb:40:in `logging_query_plan'
from /Users/phycom06/.rvm/gems/ruby-1.9.3-p429/gems/activerecord-3.2.2/lib/active_record/querying.rb:37:in `find_by_sql'
from /Users/phycom06/.rvm/gems/ruby-1.9.3-p429/gems/activerecord-3.2.2/lib/active_record/relation.rb:171:in `exec_queries'
from /Users/phycom06/.rvm/gems/ruby-1.9.3-p429/gems/activerecord-3.2.2/lib/active_record/relation.rb:160:in `block in to_a'
from /Users/phycom06/.rvm/gems/ruby-1.9.3-p429/gems/activerecord-3.2.2/lib/active_record/explain.rb:33:in `logging_query_plan'
from /Users/phycom06/.rvm/gems/ruby-1.9.3-p429/gems/activerecord-3.2.2/lib/active_record/relation.rb:159:in `to_a'
from /Users/phycom06/.rvm/gems/ruby-1.9.3-p429/gems/activerecord-3.2.2/lib/active_record/relation/finder_methods.rb:159:in `all'
from (irb):2
from /Users/phycom06/.rvm/gems/ruby-1.9.3-p429/gems/railties-3.2.2/lib/rails/commands/console.rb:47:in `start'
from /Users/phycom06/.rvm/gems/ruby-1.9.3-p429/gems/railties-3.2.2/lib/rails/commands/console.rb:8:in `start'
from /Users/phycom06/.rvm/gems/ruby-1.9.3-p429/gems/railties-3.2.2/lib/rails/commands.rb:41:in `<top (required)>'
from script/rails:6:in `require'
from script/rails:6:in `<main>'1.9.3-p429 :003 >
首先，Class是Ruby中的保留字，因此您将无法将其用作模型名称。
所以选择一个不同的名字。在这种情况下，我做了Clazz。
至于数据模型—是的，您可以在ActiveRecord类定义中指定关系，而不是在迁移中。
不清楚你的Clazz模型是什么样子的。但我假设它有2列:name和user_role_id。您可能想要将名称拉出到单独的表中，并将其替换为clazz_id -但现在我们将保持它的平直。
我将使用实例方法来构建关联，但是您可能会在has_many定义中变得疯狂。
class Clazz < ActiveRecord::Base
belongs_to :user_role
end
class User
#== Associations
has_many :user_roles, :dependent => :destroy
has_many :roles, :through => :user_roles
#== Instance Methods
def student_classes(clazz_name)
member_classes(clazz_name, Role::STUDENT)
end
def teacher_classes(clazz_name)
member_classes(clazz_name, Role::TEACHER)
end
private
def member_classes(clazz_name, type)
Clazz
.joins(:user_role)
.where(["user_role.user_id = ?", id])
.joins("INNER JOIN roles ON roles.id = user_roles.role_id")
.where("roles.name = ?", type)
.where("clazzes.name = ?", clazz_name)
end
end
class UserRole
has_many :clazzes, :dependent => :destroy
end
class Role
has_many :user_roles, :dependent => :destroy
end
你可以这样做:
user = User.find(99) # we know this user is a student
user.student_classes('Social Studies 101').all
差不多。