From: Perry Smith <pedz@...>
Date: 2008-02-01T02:33:12+09:00
Subject: weird binding error

# Below is code that represents the code I am working on.  The line
# that reads temp.wrap_with_combined is the problem.  I am not sure if
# this is a bug in my brain, Rails, or Ruby.  And, I'm stumped as to
# how to continue to debug it.
#
# At the point temp.wrap_with_combined is called, temp is a
# Cached::Queue according to the dump_me output.  The dump_me code and
# its output are included here.  According to the debugging output,
# temp is a Cached::Queue but instead of calling wrap_with_combined in
# Cached::Queue or Cached::Base, it calls wrap_with_combined in
# Object.  I can see this from the debug output.
#
# I've tried moving the def of wrap_with_combined in Cached::Base so
# it gets defined when the subclass is defined.  I've tried many
# things but it always ends up calling Object#wrap.
#
# Another clue is, I replace the temp.wrap call with this:
#                  dump_me(temp)
#                  m = temp.class.instance_method(:wrap_with_combined)
#                  m.bind(temp).call
#
# But I get this error:
# ActionView::TemplateError (bind argument must be an instance of
Cached::Queue) on line #6 of retain/favorite_queues/new.html.erb:
#
# So, while the debug says I have a Cached::Queue, the internals of
# Ruby say that I do not.
#
# I've tried to make a simple testcase to show this but I have not
# been able to.  If ActiveRecord::Base is replaced with a simple base,
# the problem goes away.  Or if the Cached::Queue is created directly,
# the problem goes away.
#
# Any ideas?
#

class Object
  def wrap_with_combined
    logger.debug "Object wrap returns self"
    self
  end
end

class Cached::Base < ActiveRecord::Base
  def wrap_with_combined
    logger.debug "Cached::Base wrap returns wrapped object"
    wrap_object(self)
  end

  def self.inherited(subclass)
    super(subclass)
    subclass.class_eval {
      def wrap_with_combined
        logger.debug "Alternate place to put wrap."
        logger.debug "Cached::Base wrap returns wrapped object"
        wrap_object(self)
      end
    }
  end
end

class Cached::Queue < Cached::Base
  # ...
end

class WrappedBase
  def self.inherited(subclass)
    super(subclass)
    subclass.class_eval {
      # Define getter methods for each association
      db_associations.each do |name|
        eval("def #{name}
                temp = @cached.#{name}
                unless temp && cache_valid
                  call_load
                  temp = @cached.#{name}
                end
                dump_me(temp)
                # Problem occurs here  wrap calls Object#wrap instead
                # of Cached::Base#wrap or Cached::Queue#wrap
                temp.wrap_with_combined
              end", nil, __FILE__, __LINE__)
        end

      def dump_me(obj)
        klass = obj.class
        return if klass.nil?
        logger.debug("DMP: 1 class=#{klass} name=#{klass.name}
methods=#{klass.instance_methods(false).inspect}")
        klass = klass.superclass
        return if klass.nil?
        logger.debug("DMP: 2 class=#{klass} name=#{klass.name}
methods=#{klass.instance_methods(false).inspect}")
        klass = klass.superclass
        return if klass.nil?
        logger.debug("DMP: 3 class=#{klass} name=#{klass.name}
methods=#{klass.instance_methods(false).inspect}")
        klass = klass.superclass
        return if klass.nil?
        logger.debug("DMP: 4 class=#{klass} name=#{klass.name}
methods=#{klass.instance_methods(false).inspect}")
        klass = klass.superclass
        return if klass.nil?
        logger.debug("DMP: 5 class=#{klass} name=#{klass.name}
methods=#{klass.instance_methods(false).inspect}")
      end
    }
  end
end

class WrappedQueue < WrappedBase
  # ...
end

# DMP: 1 class=Cached::Queue name=Cached::Queue
methods=["wrap_with_combined", "favorite_queues", "favorite_queue_ids",
"favorite_queues=", "calls", "call_ids", "favorite_queue_ids=",
"validate_associated_records_for_favorite_queues", "calls=",
"call_ids=", "validate_associated_records_for_calls"]
# DMP: 2 class=Cached::Base name=Cached::Base methods=["to_combined"]
# DMP: 3 class=ActiveRecord::Base name=ActiveRecord::Base
methods=["to_param", "increment", "readonly!", "allow_concurrency",
"destroy", "default_timezone", "record_timestamps", "quoted_id",
"reload", "save_without_transactions", "save!", "update_attributes",
"valid?", "update_attributes!", "verification_timeout",
"attributes_before_type_cast", "colorize_logging", "new_record?",
"logger", "id_before_type_cast", "save_without_transactions!", "eql?",
"toggle!", "pluralize_table_names", "valid_without_callbacks?", "id",
"[]", "attribute_present?", "inspect", "column_for_attribute", "[]=",
"save_without_validation", "decrement!", "update_attribute", "frozen?",
"id=", "hash", "update_attribute_without_validation_skipping",
"table_name_suffix", "connection", "configurations",
"save_without_validation!", "toggle", "becomes", "attribute_names",
"readonly?", "clone", "increment!", "attribute_for_inspect",
"attribute_types_cached_by_default", "table_name_prefix", "attributes",
"freeze", "save", "schema_format", "decrement",
"destroy_without_callbacks", "==", "has_attribute?", "attributes=",
"primary_key_prefix_type", "lock_optimistically",
"destroy_without_transactions"]
# DMP: 4 class=Object name=Object methods=["subclasses_of",
"require_or_load", "require", "to_yaml_style", "wrap_with_combined",
"with_options", "require_association", "copy_instance_variables_from",
"to_yaml_properties", "duplicable?", "instance_exec", "load",
"unloadable", "taguri", "to_json", "blank?", "require_dependency",
"to_query", "instance_values", "dclone", "remove_subclasses_of",
"extend_with_included_modules_from", "taguri=", "to_yaml", "`",
"to_param", "returning", "extended_by", "unwrap_to_cached", "send!",
"acts_like?"]
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