postgresql Rails“ActiveRecord_Associations_CollectionProxy 的未定义方法”
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Rails "undefined method for ActiveRecord_Associations_CollectionProxy"
提问by
I have this models:
我有这个模型：
class Student < ActiveRecord::Base
has_many :tickets
has_many :movies, through: :tickets
end
class Movie < ActiveRecord::Base
has_many :tickets, dependent: :destroy
has_many :students, through: :tickets
belongs_to :cinema
end
class Ticket < ActiveRecord::Base
belongs_to :movie, counter_cache: true
belongs_to :student
end
class Cinema < ActiveRecord::Base
has_many :movies, dependent: :destroy
has_many :students, through: :movies
has_many :schools, dependent: :destroy
has_many :companies, through: :yard_companies
end
class School < ActiveRecord::Base
belongs_to :company
belongs_to :student
belongs_to :cinema, counter_cache: true
end
class Teacher < ActiveRecord::Base
belongs_to :movie, counter_cache: true
belongs_to :company
end
class Contract < ActiveRecord::Base
belongs_to :company
belongs_to :student
end
class Company < ActiveRecord::Base
has_many :teachers
has_many :movies, through: :teachers
has_many :contracts
has_many :students, through: :contracts
end
If I write this in my movies_controller.rb:
如果我在我的movies_controller.rb 中写这个：
@students = @movie.cinema.companies.students.all
@students = @movie.cinema.companies.students.all
I have this error:
我有这个错误：
undefined method 'students' for #Company::ActiveRecord_Associations_CollectionProxy:0x00000007f13d88>
#Company::ActiveRecord_Associations_CollectionProxy:0x00000007f13d88> 的未定义方法“学生”
If instead I write this:
如果我写这个：
@students = @movie.cinema.companies.find(6).students.all
@students = @movie.cinema.companies.find(6).students.all
it shows me the correct students in my select_collection.
它向我显示了我的 select_collection 中正确的学生。
How to better understand this process?
如何更好地理解这个过程？
UPDATE:
更新：
I need the collection_select of every students in companies of a cinema of this movie.
我需要这部电影的电影院公司的每个学生的collection_select。
How to write?
怎么写？
采纳答案by Matt
As described by Nerminyou're trying to request a collection of children, from a collection of children.
正如Nermin所描述的，您试图从一组儿童中请求一组儿童。
You could use collectto gather the students from the companies along the lines of:
您可以使用以下collect方式从公司收集学生：
@movie.cinema.companies.collect(&:students).flatten.uniq
But I think you would do better to add a scope to your Student model along the lines of:
但我认为您最好按照以下方式为您的学生模型添加一个范围：
scope :for_companies, ->(_companies) {joins(:companies).where(company: _companies)}
Called with Student.for_companies(@movie.cinema.companies)
与 Student.for_companies(@movie.cinema.companies)
Disclaimer: untested, but should be a starting point!
免责声明：未经测试，但应该是一个起点！
回答by Nermin
@students = @movie.cinema.companies.students.allto explain why this throws error
@students = @movie.cinema.companies.students.all解释为什么这会引发错误
@movie.cinemawill give you cinema of the movie
@movie.cinema会给你电影的电影院
@movie.cinema.companieswill give you a list of companies for that cinema as an ActiveRecord_Association_CollectionProxy
@movie.cinema.companies将为您提供该电影院的公司列表作为 ActiveRecord_Association_CollectionProxy
Then when you call studentson the CollectionProxyof companies via @movie.cinema.companies.studentsit throws an error because CollectionProxyhas no such method.
然后当你调用students上CollectionProxy通过的公司@movie.cinema.companies.students，它抛出一个错误，因为CollectionProxy没有这样的方法。
@students = @movie.cinema.companies.find(6).students.allwill work because you get a list of companies, then from that list you find a single company with id 6 and list all students for that single company.
@students = @movie.cinema.companies.find(6).students.all会起作用，因为您获得了公司列表，然后从该列表中找到 ID 为 6 的单个公司并列出该单个公司的所有学生。
