Rails多态关联不起作用

Question

I have model with polymorphic association.

class Tag < ActiveRecord::Base
  #attributes target_id, target_type
  belongs_to :target, polymorphic: true
end

And Target model, which is user.

class User < ActiveRecord::Base
  has_many :tags, as: :target
end

But method @user = User.find params[:id]; @user.tags @user = User.find params[:id]; @user.tags returns #<ActiveRecord::Associations::CollectionProxy []> while Tag.where(target_id: @user.id, target_type: 'User') returns some objects I except.

What's wrong?

Answer 1

这是错误的方法，因为它会给NameError: undefined local variable or method user for main:Object提供错误NameError: undefined local variable or method user for main:Object ，首先您必须找到user，并且其标签如下：

@user=User.find(1)

@user.tags

Answer 2

From an instance of the User model, you can retrieve a collection of tags like this:

@user = User.find(params[:id])
@user.tags

Similarly, if you have an instance of the Tag model, you can get to its parent:

@tag.target

Answer 3

Problem was solved!

I just add to model foreign_key .

class User < ActiveRecord::Base
  has_many :tags, as: :target,
                  foreign_key: target_id
end

Thanks everyone, who try to help.