class Topic < ActiveRecord::Base
belongs_to :user, :counter_cache => true, :inverse_of => :topics
...
end
Ruby-Doc: If you are using a belongs_to on the join model, it is a good idea to set the :inverse_of option on the belongs_to, which will mean that the following example works correctly (where tags is a has_many :through association):
@post = Post.first
@tag = @post.tags.build :name => "ruby"
@tag.save
The last line ought to save the through record (a Taggable). This will only work if the :inverse_of is set:
class Taggable < ActiveRecord::Base
belongs_to :post
belongs_to :tag, :inverse_of => :taggings
end
还是不太明白。。。
无引用文章
今天就遇到了这个
class Agreement < ActiveRecord::Base
has_many :fees
end
class Fee < ActiveRecord::Base
belongs_to :agreement
validates_presence_of :target_id, :unless => proc{|fee| fee.agreement.try(:step) == 'choose_services' }
validates_presence_of :price
end
# in controller
@agremeent = Agreement.new
@agreement.step = "choose_services"
@agreement.fees.build :price => 1
@agreement.valid?
这个时候得出的结果 是false，因为 agreement还没有持久化，在Model Fee里的验证中 "fee.agreement.try(:step) " 返回的是空 因为 fee.agreement是nil。 (没有持久化的关联对象的形成比较复杂。)
那么这个验证的结果就出错了
加上inverse_of
class Agreement < ActiveRecord::Base
has_many :fees, :inverse_of => :agreement
end
再执行以上代码，
@agreement.valid? 返回 true
懂了吗？
