Wrong class_name in polymorphic association

[tomlobato]

Following https://sequel.jeremyevans.net/rdoc/files/doc/advanced_associations_rdoc.html#label-Polymorphic+Associations I`m trying to set the below relations on a legacy Mariadb database, with Sequel 5.53.0 and ruby 3.0.3:

class Comment < Sequel::Model
  many_to_one :author, reciprocal: :comments,

    setter: (lambda do |author|
      self[:author_id] = (author.pk if author)
      self[:author_type] = (author.class.name if author)
    end),
  
    dataset: (proc do
      klass = author_type.constantize
      klass.where(klass.primary_key=>author_id)
    end),
  
    eager_loader: (lambda do |eo|
      id_map = {}
      eo[:rows].each do |comment|
        comment.associations[:author] = nil 
        ((id_map[comment.author_type] ||= {})[comment.author_id] ||= []) << comment
      end
      id_map.each do |klass_name, id_map|
        klass = klass_name.constantize
        klass.where(klass.primary_key=>id_map.keys).all do |rec|
          id_map[rec.pk].each do |comment|
            comment.associations[:author] = rec
          end
        end
      end
    end)
end

class User < Sequel::Model
  one_to_many :comments, key: :author_id, reciprocal: :author, conditions: {author_type: 'User'},
    adder: lambda{|comment| comment.update(author_id: pk, author_type: 'User')},
    remover: lambda{|comment| comment.update(author_id: nil, author_type: nil)},
    clearer: lambda{comments_dataset.update(author_id: nil, author_type: nil)}
end

class Admin < Sequel::Model
  one_to_many :comments, key: :author_id, reciprocal: :author, conditions: {author_type: 'Admin'},
    adder: lambda{|comment| comment.update(author_id: pk, author_type: 'Admin')},
    remover: lambda{|comment| comment.update(author_id: nil, author_type: nil)},
    clearer: lambda{comments_dataset.update(author_id: nil, author_type: nil)}
end

When I run Comment.last.author I got NameError: uninitialized constant Author from 3.0.0/gems/activesupport-7.0.4/lib/active_support/inflector/methods.rb:280:in constantize.
If I set Author = User before Comment.last.author, it works fine.
It looks like lib/sequel/model/associations.rb is not trying to resolve the constant name dinamically., but getting it directly from many_to_one :author ....
Hints to fix are welcome.

[jeremyevans]

Thanks for the report. Looks like this example code was written before multiple reciprocal types were supported. It gives an exception trying to determine the reciprocal type, because the default behavior for that is to look at the associations of the associated class, and there is no associated class in this case.

Changing:

  many_to_one :author, reciprocal: :comments,

to:

   many_to_one :author, reciprocal: :comments, reciprocal_type: :one_to_many,

Fixes things. I'll update the documentation. Here's a more complete example testing that all parts work:

DB.create_table(:comments) do
  primary_key :id
  Integer :author_id
  String :author_type
end

DB.create_table(:users) do
  primary_key :id
end

DB.create_table(:admins) do
  primary_key :id
end

Sequel.extension :inflector

class Comment < Sequel::Model
  many_to_one :author, reciprocal: :comments, reciprocal_type: :one_to_many,

    setter: (lambda do |author|
      self[:author_id] = (author.pk if author)
      self[:author_type] = (author.class.name if author)
    end),
  
    dataset: (proc do
      klass = author_type.constantize
      klass.where(klass.primary_key=>author_id)
    end),
  
    eager_loader: (lambda do |eo|
      id_map = {}
      eo[:rows].each do |comment|
        comment.associations[:author] = nil 
        ((id_map[comment.author_type] ||= {})[comment.author_id] ||= []) << comment
      end
      id_map.each do |klass_name, id_map|
        klass = klass_name.constantize
        klass.where(klass.primary_key=>id_map.keys).all do |rec|
          id_map[rec.pk].each do |comment|
            comment.associations[:author] = rec
          end
        end
      end
    end)
end

class User < Sequel::Model
  one_to_many :comments, key: :author_id, reciprocal: :author, conditions: {author_type: 'User'},
    adder: lambda{|comment| comment.update(author_id: pk, author_type: 'User')},
    remover: lambda{|comment| comment.update(author_id: nil, author_type: nil)},
    clearer: lambda{comments_dataset.update(author_id: nil, author_type: nil)}
end

class Admin < Sequel::Model
  one_to_many :comments, key: :author_id, reciprocal: :author, conditions: {author_type: 'Admin'},
    adder: lambda{|comment| comment.update(author_id: pk, author_type: 'Admin')},
    remover: lambda{|comment| comment.update(author_id: nil, author_type: nil)},
    clearer: lambda{comments_dataset.update(author_id: nil, author_type: nil)}
end

comment = Comment.create
user = User.create
admin = Admin.create
p user.comments
p admin.comments

p comment

comment.author = user
p comment
comment.save
p comment.reload.author
p Comment.eager(:author).all.map{|c| [c, c.associations]}
p User.eager(:comments).all.map{|c| [c, c.associations]}
p Admin.eager(:comments).all.map{|c| [c, c.associations]}

comment.author = admin
p comment
p admin.associations
comment.save
p comment.reload.author
p Comment.eager(:author).all.map{|c| [c, c.associations]}
p User.eager(:comments).all.map{|c| [c, c.associations]}
p Admin.eager(:comments).all.map{|c| [c, c.associations]}

admin.remove_comment(comment)
p comment.reload
user.add_comment(comment)
p comment.reload
user.remove_comment(comment)
p comment.reload
admin.add_comment(comment)
p comment.reload
admin.remove_all_comments
p comment.reload
user.add_comment(comment)
p comment.reload
user.remove_all_comments
p comment.reload

[tomlobato]

Perfect, Jeremy, worked great!
Thank you.