I'd like to suggest an extension to the signature of stdlib Forwardable#def_instance_delegator
currently (ruby 2.3.3) it is declared as:
def_instance_delegator(accessor, method, ali = method)
I'd like to add a nil: option like this:
def_instance_delegator(accessor, method, ali = method, nil_behaviour:NoMethodError)
As of ruby2.3, delegated methods fail with
#<NoMethodError: undefined methodfoo' for nil:NilClass>`
when the declared accessor returns nil
aka, when the delegator may be nil,
the Forwardable module can not be used,
but one has to ressort to implement the forward manually.
Adding an option to the signature could solve this.
I believe that this can be implemented in a fully backward compatible way.
I named this option :nil in my example,
(some people will cry out loud)
if accessor.nil? case nil_behaviour when nil then nil # return nil, when accessor was nil when Error # raise that Error with proper args when Proc # invoke that Proc with proper args when String # return that string else # return that object end
#3 [ruby-core:82975] Updated by matz (Yukihiro Matsumoto) 11 months ago
- Status changed from Open to Feedback
The proposed solution seems to be too generic. Show us the use-case except for
nil for nil'. For example, it is acceptable thatallow_nil: true` keyword argument we see in ActiveSupport.