Extensions to nil which allow for more helpful error messages for people who are new to Rails.
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:
$ rails 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 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/json/encoding.rb, line 175 def as_json(options = nil) AS_JSON end
nil is blank:
nil.blank? # => true
# File lib/active_support/core_ext/object/blank.rb, line 45 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 39 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 50 def try(*args) nil end
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