Bug #13781
closed
Should the safe navigation operator invoke `nil?`
Added by ioquatix (Samuel Williams) over 6 years ago.
Updated over 6 years ago.
Description
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.
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
if foo
or foo ? bar : baz
) do not call nil?
or ==(nil)
, they simply do a straight comparison with nil
and false
. That's the way it should be for the safe navigation operator too.
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
versus Activerecord
if u.try!(:profile).try!(:thumbnails).try!(: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).
https://bugs.ruby-lang.org/issues/11537
- Status changed from Open to Closed
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