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
# File activerecord/lib/active_record/attribute_methods.rb, line 174 def attribute_method?(attribute) super || (table_exists? && column_names.include?(attribute.to_s.sub(/=$/, ''))) end
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"]
# File activerecord/lib/active_record/attribute_methods.rb, line 186 def attribute_names @attribute_names ||= if !abstract_class? && table_exists? column_names else [] end end
# File activerecord/lib/active_record/attribute_methods.rb, line 153 def class_method_defined_within?(name, klass, superklass = klass.superclass) # :nodoc if klass.respond_to?(name, true) if superklass.respond_to?(name, true) klass.method(name).owner != superklass.method(name).owner else true end else false end end
Returns the column object for the named attribute. Returns nil if the named attribute does not exist.
class Person < ActiveRecord::Base end person = Person.new person.column_for_attribute(:name) # the result depends on the ConnectionAdapter # => #<ActiveRecord::ConnectionAdapters::Column:0x007ff4ab083980 @name="name", @sql_type="varchar(255)", @null=true, ...> person.column_for_attribute(:nothing) # => nil
# File activerecord/lib/active_record/attribute_methods.rb, line 206 def column_for_attribute(name) column = columns_hash[name.to_s] if column.nil? ActiveSupport::Deprecation.warn(" `#column_for_attribute` will return a null object for non-existent columns in Rails 5. Use `#has_attribute?` if you need to check for an attribute's existence. ".squish) end column end
A class method is 'dangerous' if it is already (re)defined by Active Record, but not by any ancestors. (So 'puts' is not dangerous but 'new' is.)
# File activerecord/lib/active_record/attribute_methods.rb, line 149 def dangerous_class_method?(method_name) BLACKLISTED_CLASS_METHODS.include?(method_name.to_s) || class_method_defined_within?(method_name, Base) end
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
# File activerecord/lib/active_record/attribute_methods.rb, line 113 def instance_method_already_implemented?(method_name) if dangerous_attribute_method?(method_name) raise DangerousAttributeError, "#{method_name} is defined by Active Record. Check to make sure that you don't have an attribute or method with the same name." end if superclass == Base super else # If ThisClass < ... < SomeSuperClass < ... < Base and SomeSuperClass # defines its own attribute method, then we don't want to overwrite that. defined = method_defined_within?(method_name, superclass, Base) && ! superclass.instance_method(method_name).owner.is_a?(GeneratedAttributeMethods) defined || super end end
© 2004–2017 David Heinemeier Hansson
Licensed under the MIT License.