ruby syntactic sugar: dealing with nils

Question

probably asked already but I couldn\'t find it.. here are 2 common situation (for me while programming rails..) that are frustrating to write in ruby:

\"a string         


        

Answer 1

"a string".match(/foo(bar)/).to_a[1]

NilClass#to_a returns an empty array, and indexing outside of it gives you nil values.

Alternatively (what I do) you can splat the matches:

_, some, more = "a string".match(/foo(bar)(jim)/).to_a

Answer 2

In Ruby on Rails you have the try method available on any Object. According to the API:

Invokes the method identified by the symbol method, passing it any arguments and/or the block specified, just like the regular Ruby Object#send does.

Unlike that method however, a NoMethodError exception will not be raised and nil will be returned instead, if the receiving object is a nil object or NilClass.

So for the first question you can do this:

"a string".match(/abc(.+)abc/).try(:[], 1)

And it will either give you [1] or nil without error.

Answer 3

For the first I'd recommend ick's maybe (equivalent to andand)

"a string".match(/abc(.+)abc/).maybe[1]

I am not sure I understand the second one, you want this?

var = something.very.long.and.tedious.to.write || something.other

Answer 4

For the first question, I think Bob's answer is good.

For the second question,

var = something.very.long.and.tedious.to.write.instance_eval{nil? ? something.other : self}

Answer 5

Forget that Python atavism!

"a string"[/abc(.+)abc/,1] # => nil

Answer 6

"a string"[/abc(.+)abc/, 1]
# => nil
"abc123abc"[/abc(.+)abc/, 1]
# => "123"

And:

var = something.very.long.and.tedious.to.write || something.other

Please note that or has a different operator precedence than || and || should be preferred for this kind of usage. The or operator is for flow control usage, such as ARGV[0] or abort('Missing parameter').