Question

我希望能够为每个用户分配多个角色并使用User.first.roles之类的东西将它们取回，但是我迷路了，你会怎么用rails console做到这一点？我在模特中做错了什么？

u = User.first

User Load (0.1ms)  SELECT "users".* FROM "users" LIMIT 1
 => #<User id: 18 [...]>

1.9.3-p194 :004 > u.roles
NameError: uninitialized constant User::Assignment
    from [path]/ruby-1.9.3-p194/gems/activerecord-3.2.3/lib/active_record/inheritance.rb:119:in `compute_type'
    from [path]/ruby-1.9.3-p194/gems/activerecord-3.2.3/lib/active_record/reflection.rb:172:in `klass'
    from [path]/ruby-1.9.3-p194/gems/activerecord-3.2.3/lib/active_record/reflection.rb:385:in `block in source_reflection'
    from [path]/ruby-1.9.3-p194/gems/activerecord-3.2.3/lib/active_record/reflection.rb:385:in `collect'
    from [path]/ruby-1.9.3-p194/gems/activerecord-3.2.3/lib/active_record/reflection.rb:385:in `source_reflection'
    from [path]/ruby-1.9.3-p194/gems/activerecord-3.2.3/lib/active_record/reflection.rb:508:in `check_validity!'
    from [path]/ruby-1.9.3-p194/gems/activerecord-3.2.3/lib/active_record/associations/association.rb:26:in `initialize'
    from [path]/ruby-1.9.3-p194/gems/activerecord-3.2.3/lib/active_record/associations/collection_association.rb:24:in `initialize'
    from [path]/ruby-1.9.3-p194/gems/activerecord-3.2.3/lib/active_record/associations/has_many_through_association.rb:10:in `initialize'
    from [path]/ruby-1.9.3-p194/gems/activerecord-3.2.3/lib/active_record/associations.rb:157:in `new'
    from [path]/ruby-1.9.3-p194/gems/activerecord-3.2.3/lib/active_record/associations.rb:157:in `association'
    from [path]/ruby-1.9.3-p194/gems/activerecord-3.2.3/lib/active_record/associations/builder/association.rb:44:in `block in define_readers'
    from (irb):4
    from [path]/ruby-1.9.3-p194/gems/railties-3.2.3/lib/rails/commands/console.rb:47:in `start'
    from [path]/ruby-1.9.3-p194/gems/railties-3.2.3/lib/rails/commands/console.rb:8:in `start'
    from [path]/ruby-1.9.3-p194/gems/railties-3.2.3/lib/rails/commands.rb:41:in `<top (required)>'
    from script/rails:6:in `require'
    from script/rails:6:in `<main>'

模型/ user.rb

class User < ActiveRecord::Base
 attr_accessible :name, :email, :password, :password_confirmation, :role_id
 has_many :assignments
 has_many :roles, through: :assignments
 #more code...
end

模型/ role.rb

class Role < ActiveRecord::Base
 attr_accessible :name
 has_many :assignments
 has_many :users, through: :assignments
end

模型/ assignments.rb

class Assignments < ActiveRecord::Base
 attr_accessible :role_id, :user_id
 belongs_to :user
 belongs_to :role
end

schema.rb：http://cl.ly/323n1t0Q1t390y1M2S0E

Answer 1

将模型文件models/assignments.rb的名称更改为models/assignment.rb，并将其类名从class Assignments更改为class Assignment。模型名称应该是单一的轨道约定。因此，当您运行u.roles时，它正在寻找分配而不是分配。

用户通过作业有很多角色

1 个答案: