Ruby syntactic sugar for chains of (!obj.nil?)

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Is there a clean way to avoid calling a method on nil in a nested params hash?
Is there an equivalent null prevention on chained attributes of groovy in ruby?

Is there any syntactic sugar, in Ruby, that help avoiding "undefined method `xx' for nil:NilClass" without writing this?

if !something.nil? && !something.very.nil? && !something.very.long.nil? && !something.very.long.to.nil? then
   if something.very.long.to.write != 0 then
    ...
   end
end

in Groovy I'll do this

if(something?.very?.loong?.to?.write != 0)

Is there an equivalent syntax for Ruby?

Also http://stackoverflow.com/questions/11164004/does-ruby-have-syntax-for-safe-navigation-operator-of-nil-values-like-in-groovy from 4 days ago — tim_yates, Jun 27 '12 at 10:28
Thanks, it was hard to search in the tons of Ruby questions... — , Jun 27 '12 at 10:43
also http://stackoverflow.com/questions/5429790/is-there-a-clean-way-to-avoid-calling-a-method-on-nil-in-a-nested-params-hash. In a nutshell: `andand` or `maybe` (ick). — tokland, Jun 27 '12 at 12:15

score 1 · Answer 1 · answered Jun 27 '12 at 10:31

1

It's a duplicate question, but I can't find that for the moment. My way is:

if a = something and a = a.very and a = a.long and a = a.to
  if a = a.write
    ...
  end
end

answered Jun 27 '12 at 10:31

sawa

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Not sweet enough, I need more sugar ;-) Groovy 1 : Ruby 0 – Jun 27 '12 at 10:36
ouch, this "a" may get real dizzy with some many value destructive changes :-p – tokland Jun 27 '12 at 12:16
@tokland If a distructive operation appears within the sequence, you can take `a.dup` to continue. – sawa Jun 27 '12 at 13:28

score 0 · Answer 2 · answered Jun 27 '12 at 10:34

class Object
  def try(*a, &b)
    if a.empty? && block_given?
      yield self
    else
      __send__(*a, &b)
    end
  end
end

class NillClass
  def try(*args)
    nil
  end
end

Then in your case

if result = something.try(:very).try(:long).try(:to).try(:write)
  if result != 0
  end
end

Ruby syntactic sugar for chains of (!obj.nil?)

2 Answers2