0

Greetings good people!

I want to link 2 models through another model:

class Article < ActiveRecord::Base
  ...some callbacks...

  has_many :article_images, dependent: :destroy
  has_many :images, through: :article_images

  ...some methods...
end

class Image < ActiveRecord::Base
  ...some callbacks...

  has_many :article_images, dependent: :destroy
  has_many :articles, through: :article_images

  ...other methods...
end

class ArticleImage < ActiveRecord::Base
  belongs_to :article
  belongs_to :image
end

This works fine when I try to relate an article with an image using << or create():

art = Article.find 2 #=> <Article id: 2, category: 14, template: 2, param: "2">    
art.images #=> <ActiveRecord::Associations::CollectionProxy []

img = Image.find 2 #=> <Image id: 2, filename: "testna2.jpg">   
art.images << img #=> <ActiveRecord::Associations::CollectionProxy [#<Image id: 2, filename: "testna2.jpg">]>

The problem occurs when I try to do this the other way around:

img = Image.find 2
img.articles #=> ArgumentError: wrong number of arguments (1 for 0)

I didn't even come to the part where I assign an image object to a the article, looks like the association only works in one direction - art.images returns a collection, but img.articles causes an error.

Here's the crucial part of my schema (using mySQL):

create_table "articles", force: true do |t|
  t.integer "category"
  t.integer "template"
  t.string  "param"
end

create_table "article_images", force: true do |t|
  t.integer "article_id"
  t.integer "image_id"
  t.string  "lang"
  t.string  "title"
  t.text    "desc"
end

create_table "images", force: true do |t|
  t.string "filename"
end

Here's the trace (seems like the problem isn't caused by my models?):

2.0.0p247 :023 > img.articles
ArgumentError: wrong number of arguments (1 for 0)
    from /home/ziga/.rvm/gems/ruby-2.0.0-p247@goopti-storefront/gems/activerecord-4.0.0/lib/active_record/associations/builder/association.rb:70:in `articles'
from (irb):23
from /home/ziga/.rvm/gems/ruby-2.0.0-p247@goopti-storefront/gems/railties-4.0.0/lib/rails/commands/console.rb:90:in `start'
from /home/ziga/.rvm/gems/ruby-2.0.0-p247@goopti-storefront/gems/railties-4.0.0/lib/rails/commands/console.rb:9:in `start'
from /home/ziga/.rvm/gems/ruby-2.0.0-p247@goopti-storefront/gems/railties-4.0.0/lib/rails/commands.rb:64:in `<top (required)>'
from bin/rails:4:in `require'
from bin/rails:4:in `<main>'

Does anyone have a clue what's going on? At first I used has_and_belongs_to_many to connect the Article and Image models, but then I figured it would be better to include a third model with some extra columns (apart from the ids). That doesn't seem to be such a good idea now...

4

1 回答 1

0

好的，看起来我找到了导致错误的原因，但我仍然不确定为什么 - 我在我的代码中使用了attr_accessor，看起来问题出在它的名称上。

我改变了

attr_accessor :association

进入

attr_accessor :assoc

我的问题突然消失了，尽管使用@association变量的方法甚至在我重命名之前就被注释掉了。

我仍然不确定attr_accessor如何影响模型和关联，但我认为“关联”可能是 rails 中的保留字（虽然在任何列表中都找不到）。

如果有人遇到同样的问题，那么我建议您检查您的代码是否有可疑的 attr_accessors 或变量和方法名称。

我仍然无法对发生的事情做出最终结论，所以如果您认为您对这个问题有所了解，请发表评论:)

于 2013-11-13T10:05:45.753 回答