Nils and method chaining

Question

I\'m just breaking into the ruby world and I could use a helping hand.

Suppose b is nil.

I\'d like the following code to return n

Answer 1

You can use the inline rescue:

x = a.b.c("d").e rescue nil

x will be nil if b is nil.

Or, as someone commented in that link, you can use the andand gem (see docs):

x = a.andand.b.andand.c("d").andand.e

Answer 2

"try" is very clean, as lucapette said. More generally, you could also use a begin-rescue-end block too, depending on your situation.

begin
  a.b.c("d").e
rescue NoMethodError=>e
  return nil
end

Answer 3

I've made the may_nil gem for this. https://github.com/meesern/may_nil

Like @Sony Santos's safe_nils answer it uses a block to wrap the method chain and rescues NoMethodError, but will check for nil (and so will properly raise an exception for other classes).

require `may_nil`
may_nil {a.b.c("d").e}   => nil (or the end result)
may_nil {0.b.c("d").e}   => Exception: NoMethodError (b on Fixnum)

Unlike andand or ike's maybe you don't need to pepper the method chain.

a.andand.b.andand.c("d").andand.e
==>
may_nil{ a.b.c("d").e }