的Rails不能创建HABTM关系

Question

我有2种型号：

class Hashtag < ActiveRecord::Base 
    has_and_belongs_to_many :photos 
    attr_accessible :name 
*** 
end 

class Photo < ActiveRecord::Base 
    has_and_belongs_to_many :hashtags, :uniq => true 
*** 
end 

关系创建代码：

photo = current_user.photos.new(params[:photo]) 
if !photo.nil? and photo.save! 
    photo.text.scan(/#[[:alnum:]]+/).each do |billet| 
      next if billet.length > 25 
      hashtag = Hashtag.first_or_initialize(:name => billet) 
      if hashtag.persisted? 
       hashtag.touch 
      else 
       hashtag.save! 
      end 
      photo.hashtags << hashtag 
     end 
    render json: photo 
end 

但它不工作。看起来哈希标签永远不会被保存。这段代码有什么问题？

UPD：

加入表：

def up 
    create_table :hashtags_photos, :id => false do |t| 
     t.integer :photo_id 
     t.integer :hashtag_id 
    end 

    add_index :hashtags_photos, [:photo_id, :hashtag_id], :unique => true 
    end 

和错误：

ActiveRecord::AssociationTypeMismatch: Hashtag(#70233360314580) expected, got TrueClass(#70233335523020) 

Answer 1

权的方式来做到这一点：

text.scan(/#[[:alnum:]]+/).each do |workpiece| 
     next if workpiece.length > 25 
     hashtag = Hashtag.find_by_name(workpiece) 
     if hashtag 
      hashtag.touch 
     else 
      hashtag = Hashtag.create!(:name => workpiece) 
     end 
     hashtags << hashtag 
end