Should the safe navigation operator invoke `nil?`
In the following example:
class Later < BasicObject def initialize(&block) raise ::ArgumentError, "Block required" unless block if block.arity > 0 raise ::ArgumentError, "Cannot store a promise that requires an argument" end @block = block end def __resolve__ @result ||= @block.call end def nil? __resolve__.nil? end def respond_to?(name) __resolve__.respond_to?(name) end def method_missing(name, *args, &block) __resolve__.__send__(name, *args, &block) end end Person = Struct.new(:name, :age) person = Later.new do nil # Person.new("Froob", 200) end puts person.nil? puts person&.name
The code fails because person is a proxy object.
If safe navigation operator invoked
nil? it should work. But, it's not clear exactly how the implementation should behave, or whether it's possible to implement this style of proxy.
#1 [ruby-core:82237] Updated by marcandre (Marc-Andre Lafortune) over 1 year ago
Short answer is "no".
Longer answer is:
- is there an actual use case? I very much doubt there is one
- BasicObject does not respond to
nil?, so the safe operator would not work in that case?
- other Ruby conditional (like
foo ? bar : baz) do not call
==(nil), they simply do a straight comparison with
false. That's the way it should be for the safe navigation operator too.
#2 [ruby-core:82247] Updated by shevegen (Robert A. Heiler) over 1 year ago
is there an actual use case? I very much doubt there is one
This is what some filed issues appear to be - a mostly theoretical
view that does not appear to be likely to emerge.
When Hiroshi filed the request, I do not think that he had any
"proxy" object in mind - it was simply to avoid compound methods
check e. g:
if u && u.profile && u.profile.thumbnails && u.profiles.thumbnails.large
To be honest, I actually find the .try! variant more readable than the
&. variant but this is not the topic of course (not sure why activerecord
uses the '!' there, it also makes the chain ugly, in my opinion; perhaps
I am way too picky).