Extensions to nil
which allow for more helpful error messages
for people who are new to Rails.
#id exists in Ruby 1.8 (though it
is deprecated). Since id
is a fundamental method of Active
Record models #id is redefined as
well to raise a RuntimeError and warn the user. She probably wanted a model
database identifier and the 4 returned by the original method could result
in obscure bugs.
The flag config.whiny_nils
determines whether this feature is
enabled. By default it is on in development and test modes, and it is off
in production mode.
# File lib/active_support/whiny_nil.rb, line 15 def self.add_whiner(klass) ActiveSupport::Deprecation.warn "NilClass.add_whiner is deprecated and this functionality is " "removed from Rails versions as it affects Ruby 1.9 performance.", caller end
nil
is blank:
nil.blank? # => true
# File lib/active_support/core_ext/object/blank.rb, line 47 def blank? true end
nil
is not duplicable:
nil.duplicable? # => false nil.dup # => TypeError: can't dup NilClass
# File lib/active_support/core_ext/object/duplicable.rb, line 35 def duplicable? false end
Raises a RuntimeError when you attempt to call id
on
nil
.
# File lib/active_support/whiny_nil.rb, line 21 def id raise RuntimeError, "Called id for nil, which would mistakenly be #{object_id} -- if you really wanted the id of nil, use object_id", caller end
# File lib/active_support/core_ext/object/to_param.rb, line 9 def to_param self end
Calling try
on nil
always returns
nil
. It becomes specially helpful when navigating through
associations that may return nil
.
nil.try(:name) # => nil
Without try
@person && !@person.children.blank? && @person.children.first.name
With try
@person.try(:children).try(:first).try(:name)
# File lib/active_support/core_ext/object/try.rb, line 54 def try(*args) nil end