From 9113aa2744ef1daba403eafdbb6e6f3594acaacd Mon Sep 17 00:00:00 2001 From: David Heinemeier Hansson Date: Mon, 20 Jun 2005 11:15:46 +0000 Subject: Forgot to actually add the whiny nil git-svn-id: http://svn-commit.rubyonrails.org/rails/trunk@1455 5ecf4fe2-1ee6-0310-87b1-e25e094e27de --- activesupport/lib/active_support/whiny_nil.rb | 43 +++++++++++++++++++++++++++ 1 file changed, 43 insertions(+) create mode 100644 activesupport/lib/active_support/whiny_nil.rb (limited to 'activesupport/lib/active_support') diff --git a/activesupport/lib/active_support/whiny_nil.rb b/activesupport/lib/active_support/whiny_nil.rb new file mode 100644 index 0000000000..4a83cd585e --- /dev/null +++ b/activesupport/lib/active_support/whiny_nil.rb @@ -0,0 +1,43 @@ +# 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 + + private + def method_missing(method, *args, &block) + if @@method_class_map.include?(method) + raise_nil_warning_for @@method_class_map[method] + else + super + end + end + + def raise_nil_warning_for(klass) + raise NoMethodError, NIL_WARNING_MESSAGE % klass + 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 + -- cgit v1.2.3