1
0
Fork 0
mirror of https://github.com/rails/rails.git synced 2022-11-09 12:12:34 -05:00
rails--rails/activesupport/lib/active_support/whiny_nil.rb
David Heinemeier Hansson 117ee110d7 Improved the whiny nil #1600 [Nicholas Seckar]
git-svn-id: http://svn-commit.rubyonrails.org/rails/trunk@1660 5ecf4fe2-1ee6-0310-87b1-e25e094e27de
2005-07-04 09:54:30 +00:00

46 lines
1.5 KiB
Ruby

# Extensions to nil which allow for more helpful error messages for
# people who are new to rails.
#
# The aim is to ensure that when users pass nil to methods where that isn't
# appropriate, instead of NoMethodError and the name of some method used
# by the framework users will see a message explaining what type of object
# was expected.
class NilClass
WHINERS = [ ::ActiveRecord::Base, ::Array ]
@@method_class_map = Hash.new
WHINERS.each do |klass|
methods = klass.public_instance_methods - public_instance_methods
methods.each do |method|
@@method_class_map[method.to_sym] = klass
end
end
def id
raise RuntimeError, "Called id for nil, which would mistakenly be 4 -- if you really wanted the id of nil, use object_id", caller
end
private
def method_missing(method, *args, &block)
if @@method_class_map.include?(method)
raise_nil_warning_for @@method_class_map[method], caller
else
super
end
end
def raise_nil_warning_for(klass, with_caller = nil)
raise NoMethodError, NIL_WARNING_MESSAGE % klass, with_caller || caller
end
NIL_WARNING_MESSAGE = <<-end_message unless const_defined?(:NIL_WARNING_MESSAGE)
WARNING: You have a nil object when you probably didn't expect it! Odds are you
want an instance of %s instead.
Look in the callstack to see where you're working with an object that could be nil.
Investigate your methods and make sure the object is what you expect!
end_message
end