Our Daily Method #3: Hash.multi

Geplaatst door Remco van 't Veer do, 07 feb 2008 08:00:00 GMT

You have probably used it before; Hash.new with a block to make a two-dimensional hash;

map = Hash.new{|h,k| h[k] = {}}
map[:dragon][:strength] = 9

But sometimes you need a multi-dimensional hash;

def Hash.multi
  Hash.new{|h,k| h[k] = Hash.multi}
end

I use it in an application to construct a simple cache with complex keys;

CACHE = Hash.multi

def expensive_query(key)
  cache = CACHE[:query][auth_level][current_channel]
  unless cache.has_key?(key)
    cache[key] = Server.query(auth_level, current_channel, key) 
  else
    cache[key]
  end
end