Active Record has_many :through remove one associated record

问题

This may be a very basic oversight on my part, but I can't seem to recall a simple method for removing an association between two objects joined via has_many :through. IE:

class Photo
  has_many :tags, :through => :taggings
  has_many :taggings, :dependent => :destroy
end

class Tags
  has_many :photos, :through => :taggings
  has_many :taggings, :dependent => :destroy
end

class Taggings
  belongs_to :photo
  belongs_to :tag
end

If you have two objects, tag and photo, you can associate them just by doing this:

photo.tags << tag

So, is there an equally simple opposite to this? ie:

photo.tags.remove tag

回答1:

here's what you want:

photo.tags.delete(tag)

来源：https://stackoverflow.com/questions/13216251/active-record-has-many-through-remove-one-associated-record