Methods
A
I
Instance Public methods
attribute_method?(attribute)

Returns true if attribute is an attribute method and table exists, false otherwise.

class Person < ActiveRecord::Base
end

Person.attribute_method?('name')   # => true
Person.attribute_method?(:age=)    # => true
Person.attribute_method?(:nothing) # => false

Source: show | on GitHub 

# File activerecord/lib/active_record/attribute_methods.rb, line 98
def attribute_method?(attribute)
  super || (table_exists? && column_names.include?(attribute.to_s.sub(/=$/, '')))
end
attribute_names()

Returns an array of column names as strings if it’s not an abstract class and table exists. Otherwise it returns an empty array.

class Person < ActiveRecord::Base
end

Person.attribute_names
# => ["id", "created_at", "updated_at", "name", "age"]

Source: show | on GitHub 

# File activerecord/lib/active_record/attribute_methods.rb, line 110
def attribute_names
  @attribute_names ||= if !abstract_class? && table_exists?
      column_names
    else
      []
    end
end
instance_method_already_implemented?(method_name)

Raises a ActiveRecord::DangerousAttributeError exception when an Active Record method is defined in the model, otherwise false.

class Person < ActiveRecord::Base
  def save
    'already defined by Active Record'
  end
end

Person.instance_method_already_implemented?(:save)
# => ActiveRecord::DangerousAttributeError: save is defined by ActiveRecord

Person.instance_method_already_implemented?(:name)
# => false

Source: show | on GitHub 

# File activerecord/lib/active_record/attribute_methods.rb, line 57
def instance_method_already_implemented?(method_name)
  if dangerous_attribute_method?(method_name)
    raise DangerousAttributeError, "#{method_name} is defined by Active Record"
  end

  if superclass == Base
    super
  else
    # If B < A and A defines its own attribute method, then we don't want to overwrite that.
    defined = method_defined_within?(method_name, superclass, superclass.generated_attribute_methods)
    defined && !ActiveRecord::Base.method_defined?(method_name) || super
  end
end