Ruby on rails Rails创建M:M关系
我有一个用户模型和团队模型,并加入了一个成员模型 一个用户可以有多个团队,每个团队可以有多个用户,等等Ruby on rails Rails创建M:M关系,ruby-on-rails,activerecord,Ruby On Rails,Activerecord,我有一个用户模型和团队模型,并加入了一个成员模型 一个用户可以有多个团队,每个团队可以有多个用户,等等 class User < ApplicationRecord has_many :memberships has_many :teams, through: :memberships End class Team < ApplicationRecord has_many :memberships has_many :users, through: :members
class User < ApplicationRecord
has_many :memberships
has_many :teams, through: :memberships
End
class Team < ApplicationRecord
has_many :memberships
has_many :users, through: :memberships
End
class Membership < ApplicationRecord
belongs_to :user
belongs_to :team
end
我正在寻找一种简单地创建会员记录的方法,但是我缺少一些东西:
2.4.0 :026 > t = Team.last
Team Load (1.2ms) SELECT "teams".* FROM "teams" ORDER BY "teams"."id" DESC LIMIT $1 [["LIMIT", 1]]
=> #<Team id: 42129, name: "Reds", description: "A good team", created_at: "2017-05-18 05:05:09", updated_at: "2017-05-18 05:05:09">
2.4.0 :027 > User.first.memberships
User Load (1.7ms) SELECT "users".* FROM "users" ORDER BY "users"."id" ASC LIMIT $1 [["LIMIT", 1]]
Membership Load (1.1ms) SELECT "memberships".* FROM "memberships" WHERE "memberships"."user_id" = $1 LIMIT $2 [["user_id", 1], ["LIMIT", 11]]
=> #<ActiveRecord::Associations::CollectionProxy []>
2.4.0 :028 > User.first.memberships << t
User Load (0.8ms) SELECT "users".* FROM "users" ORDER BY "users"."id" ASC LIMIT $1 [["LIMIT", 1]]
(0.4ms) BEGIN
(0.4ms) ROLLBACK
ActiveRecord::AssociationTypeMismatch: Membership(#23507760) expected, got #<Team id: 42129, name: "Reds", description: "A good team", created_at: "2017-05-18 05:05:09", updated_at: "2017-05-18 05:05:09"> which is an instance of Team(#33684520)
from (irb):28
2.4.0 :029 >
我错过了什么
更新:
创建新成员资格记录并手动添加fk值时,在尝试保存时出现以下错误:
2.4.0 :037 > m
=> #<Membership id: nil, user_id: 1, team_id: 22641, created_at: nil, updated_at: nil>
2.4.0 :038 > m.save
(0.5ms) BEGIN
(0.4ms) ROLLBACK
NoMethodError: undefined method `class_name' for nil:NilClass
Did you mean? class_eval
from (irb):38
更新2
更新之前收到的第一条错误消息是,ActiveRecord需要一个成员身份实例,而它需要一个团队。User.first.teams感谢您回答了问题1。更新2对我来说毫无意义。
2.4.0 :022 > user = User.first
User Load (2.7ms) SELECT "users".* FROM "users" ORDER BY "users"."id" ASC LIMIT $1 [["LIMIT", 1]]
=> #<User id: 1, created_at: "2017-05-15 08:17:01", updated_at: "2017-05-19 02:54:30">
2.4.0 :023 > team = Team.first
Team Load (2.3ms) SELECT "teams".* FROM "teams" ORDER BY "teams"."id" ASC LIMIT $1 [["LIMIT", 1]]
=> #<Team id: 22641, name: "Reds", description: "This is a good team", created_at: "2017-05-18 01:41:00", updated_at: "2017-05-18 05:05:09">
2.4.0 :027 > Membership.delete_all
SQL (1.9ms) DELETE FROM "memberships"
=> 1
2.4.0 :029 > m=Membership.new(user: user, team: team)
=> #<Membership id: nil, user_id: 1, team_id: 22641, created_at: nil, updated_at: nil>
2.4.0 :031 > m.save
(1.0ms) BEGIN
SQL (2.3ms) INSERT INTO "memberships" ("user_id", "team_id", "created_at", "updated_at") VALUES ($1, $2, $3, $4) RETURNING "id" [["user_id", 1], ["team_id", 22641], ["created_at", "2017-05-22 03:37:22.803718"], ["updated_at", "2017-05-22 03:37:22.803718"]]
(2.1ms) COMMIT
=> true
2.4.0 :032 > Membership.delete_all
SQL (1.9ms) DELETE FROM "memberships"
=> 1
2.4.0 :033 > m=Membership.new
=> #<Membership id: nil, user_id: nil, team_id: nil, created_at: nil, updated_at: nil>
2.4.0 :034 > m.user_id=user.id
=> 1
2.4.0 :035 > m.team_id=team.id
=> 22641
2.4.0 :036 > m
=> #<Membership id: nil, user_id: 1, team_id: 22641, created_at: nil, updated_at: nil>
2.4.0 :037 > m.save
(0.5ms) BEGIN
User Load (0.9ms) SELECT "users".* FROM "users" WHERE "users"."id" = $1 LIMIT $2 [["id", 1], ["LIMIT", 1]]
(0.8ms) ROLLBACK
NoMethodError: undefined method `class_name' for nil:NilClass
Did you mean? class_eval
from (irb):37
2.2.3 :009 > user = User.first
User Load (0.2ms) SELECT "users".* FROM "users" ORDER BY "users"."id" ASC LIMIT 1
=> #<User id: 1>
2.2.3 :010 > team = Team.first
Team Load (0.2ms) SELECT "teams".* FROM "teams" ORDER BY "teams"."id" ASC LIMIT 1
=> #<Team id: 1>
2.2.3 :011 > membership = Membership.new(user: user, team: team)
=> #<Membership id: nil, user_id: 1, team_id: 1>
2.2.3 :012 > membership.save
(0.1ms) begin transaction
SQL (1.2ms) INSERT INTO "memberships" ("user_id", "team_id") VALUES (?, ?) [["user_id", 1], ["team_id", 1]]
(2.3ms) commit transaction
=> true