diff options
Diffstat (limited to 'activesupport/lib/active_support/whiny_nil.rb')
| -rw-r--r-- | activesupport/lib/active_support/whiny_nil.rb | 36 |
1 files changed, 27 insertions, 9 deletions
diff --git a/activesupport/lib/active_support/whiny_nil.rb b/activesupport/lib/active_support/whiny_nil.rb index 983a14fd42..099619191c 100644 --- a/activesupport/lib/active_support/whiny_nil.rb +++ b/activesupport/lib/active_support/whiny_nil.rb @@ -1,11 +1,29 @@ -# Extensions to nil which allow for more helpful error messages for -# people who are new to rails. +# 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. - +# Ruby raises NoMethodError if you invoke a method on an object that does not +# respond to it: +# +# $ ruby -e nil.destroy +# -e:1: undefined method `destroy' for nil:NilClass (NoMethodError) +# +# With these extensions, if the method belongs to the public interface of the +# classes in NilClass::WHINERS the error message suggests which could be the +# actual intended class: +# +# $ script/runner nil.destroy +# ... +# You might have expected an instance of ActiveRecord::Base. +# ... +# +# NilClass#id exists in Ruby 1.8 (though it is deprecated). Since +id+ is a fundamental +# method of Active Record models NilClass#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 <tt>config.whiny_nils</tt> determines whether this feature is enabled. +# By default it is on in development and test modes, and it is off in production +# mode. class NilClass WHINERS = [::Array] WHINERS << ::ActiveRecord::Base if defined? ::ActiveRecord @@ -18,7 +36,7 @@ class NilClass methods.each { |method| @@method_class_map[method.to_sym] = class_name } end - # Raises a RuntimeError when you attempt to call id on nil or a nil object. + # Raises a RuntimeError when you attempt to call +id+ on +nil+. 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 @@ -28,7 +46,7 @@ class NilClass raise_nil_warning_for @@method_class_map[method], method, caller end - # Raises a NoMethodError when you attempt to call a method on nil, or a nil object. + # Raises a NoMethodError when you attempt to call a method on +nil+. def raise_nil_warning_for(class_name = nil, selector = nil, with_caller = nil) message = "You have a nil object when you didn't expect it!" message << "\nYou might have expected an instance of #{class_name}." if class_name |