Accessing elements of nested hashes in ruby [duplicate]

Answer 1

value = structure[:a][:b] rescue nil

Answer 2

Not that I would do it, but you can Monkeypatch in NilClass#[]:

> structure = { :a => { :b => 'foo' }}
#=> {:a=>{:b=>"foo"}}

> structure[:x][:y]
NoMethodError: undefined method `[]' for nil:NilClass
        from (irb):2
        from C:/Ruby/bin/irb:12:in `<main>'

> class NilClass; def [](*a); end; end
#=> nil

> structure[:x][:y]
#=> nil

> structure[:a][:y]
#=> nil

> structure[:a][:b]
#=> "foo"

Go with @DigitalRoss's answer. Yes, it's more typing, but that's because it's safer.

Answer 3

I am currently trying out this:

# --------------------------------------------------------------------
# System so that we chain methods together without worrying about nil
# values (a la Objective-c).
# Example:
#   params[:foo].try?[:bar]
#
class Object
  # Returns self, unless NilClass (see below)
  def try?
    self
  end
end  
class NilClass
  class MethodMissingSink
    include Singleton
    def method_missing(meth, *args, &block)
    end
  end
  def try?
    MethodMissingSink.instance
  end
end

I know the arguments against try, but it is useful when looking into things, like say, params.