Ruby variable scoping can be tricky sometimes. Ruby will initialize the local variable 'foo' even though that line is never executed. Since it's now in the local scope, the method 'foo' doesn't get run during the second if.

gistfile1.rb

class Thing
  def foo
    "foo"
  end

  def bar
    puts foo
    if foo.nil?
      foo = "bar"
    end
    if foo.nil?
      foo = "baz"
    end
    puts foo
  end
end

Thing.new.bar
# >> foo
# >> baz