Does Ruby have syntax for safe navigation operator of nil values, like in Groovy?

Question

In Groovy, there is a nice syntax for working with null values.

For example, I can do an if statement:

if (obj1?.obj2?.value) {

}

This will not throw a NullPointerException even if obj1 is null (it will evaluate to false).

This is something that's very convenient, so wondering if there is a Ruby equivalent I missed.

Griffis

#8806082 – Oleneolenka

thanks! Also found the andand gem just now that tries to introduce this to ruby through a method: weblog.raganwald.com/2008/01/objectandand-objectme-in-ruby.html – Griffis

Not yet in a stable release, but the development branch of Ruby now has the .? operator. See bugs.ruby-lang.org/issues/… – Insomnia

Answer 1

In a rails app there is Object#try

So you can do

obj1.try(:obj2).try(:value)

or with a block (as said on comments bellow)

obj.try {|obj| obj.value}

UPDATE

In ruby 2.3 there is operator for this:

obj&.value&.foo

Which is the same as obj && obj.value && obj.value.foo

Decomposer

Or alternately: obj.try {|obj| obj.value} - block mode often makes more visual sense IMHO. – Harbird

This block syntax makes the most sense when you want to do something with the value like call a method on it. – Hols

A common pattern to tackle this kind of problem are null objects. – Rustle

Note that Object#try is a part of the ActiveSupport gem, which can also be used outside of Rails. – Fewer

"Which is the same as"... This is not true when obj is false. – Corbie

Thanks Jesse for the heads up – Decomposer

@Decomposer I see this equivalency stated in every resource I can find about the new operator. I posted a new question regarding this misinformation: #34602554 – Corbie

[20] pry(main)> @asd.try(:asd) NoMethodError: undefined method try' for nil:NilClass` – Brezin

@Brezin try is only available with ActiveSupport (part of Ruby on Rails) – Decomposer

Answer 2

This has been added to Ruby 2.3.

The syntax is obj1&.meth1&.meth2.

Centipoise

Answer 3

try was the only standard way to do this before Ruby 2.3. With Ruby 2.3 you can do:

if obj1&.obj2&.value

end

Also, if you have a hash structure, you can use the _. operator with Hashie:

require 'hashie'
myhash = Hashie::Mash.new({foo: {bar: "blah" }})

myhash.foo.bar
=> "blah"    

myhash.foo?
=> true

# use "underscore dot" for multi-level testing
myhash.foo_.bar?
=> true
myhash.foo_.huh_.what?
=> false

Anastassia

So, try was the only way to do this when I answered the quesiton. The &. notation was just added with Ruby 2.3. The downvote wasn't really necessary, a comment or edit would have been appreciated. – Anastassia

Not sure if your downvote was related, but I just made an edit because you were using JavaScript syntax for your if statement. – Centipoise

Answer 4

Ruby 2.3 will have support for the safe navigation operator:

obj1&.obj2&.value

https://www.ruby-lang.org/en/news/2015/11/11/ruby-2-3-0-preview1-released/

Gillman