Question

I have the following code to create an array to object hash:

tp = TupleProfile.new(98, 99)
keyDict = Hash[Array[98,99] => tp]
keyDict[[98,99]].addLatency(0.45)
puts keyDict[[98,99]].getAvg()

This works, but I’d like to be able to call addLatency without checking for an existing hash value:

keyDict[[100,98]].addLatency(0.45) #throws error right now

So I want to create a default value that varies based on the key, something like:

keyDict = Hash.new(TupleProfile.new(theKey[0], theKey[1]))

Where theKey is some sort of special directive. Is there any reasonably clean way to do this, or am I better off checking each time or making a wrapper class for the hash?

Answer 1

Try the Hash.new block notation:

keyDict = Hash.new {|hash,key| hash[key] = TupleProfile.new(*key) }

Using the standard parameter notation (Hash.new(xyz)) will really only instantiate a single TupleProfile object for the hash; this way there will be one for each individual key.