hash.delete_if { |key, value| true } doesn't delete ... why?

Answer 1

Are you certain that cache is a Hash? The behavior you are describing is not normal.

$ ruby -v
ruby 1.8.7 (2009-06-12 patchlevel 174) [universal-darwin10.0]

>> h = {:a => 1, :b => 2}
=> {:b=>2, :a=>1}
>> h
=> {:b=>2, :a=>1}
>> h.delete_if {|k,v| v == 2}
=> {:a=>1}
>> h
=> {:a=>1}

>> h = {:a => 1, :b => 2}
=> {:b=>2, :a=>1}
>> h.delete_if {|k,v| true}
=> {}
>> h
=> {}

Answer 2

Maybe it is a bug of acts_as_taggable_on and you can just fill in a bug report.