48 lines
1.4 KiB
Ruby
48 lines
1.4 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 "Called id for nil, which would mistakenly be 4 -- if you really wanted the id of nil, use object_id"
|
|
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
|
|
|