Use hash or case-statement in Ruby?

Often, when we need to get a value based on the other one, we're using a case-statement. Like this

 def realizing_trade_type(realizable_trade_type) case realizable_trade_type when 'buy' 'sell' when 'short' 'cover' when 'buy_contract' 'sell_contract' when 'short_contract' 'cover_contract' end end 

But, if the conditions and the results are simple values, why don't we use hash for this? We can :)

 REALIZING_TRADE_TYPES = { 'buy' => 'sell', 'short' => 'cover', 'buy_contract' => 'sell_contract', 'short_contract' => 'cover_contract' }.freeze 

Here is the benchmark of both options, executed 10000000 times. It shows that a hash is faster in times for such the kind of usage.

 >> require 'benchmark' true >> Benchmark.bm(15) do |x| x.report('hash') { 10_000_000.times { REALIZING_TRADE_TYPES['buy'] } } x.report('case-statement') { 10_000_000.times { realizing_trade_type 'buy' } } x.report('empty') { 10_000_000.times {} } end user system total real hash 0.990423 0.003412 0.993835 ( 1.057612) case-statement 1.752263 0.004531 1.756794 ( 1.762030) empty 0.380810 0.000728 0.381538 ( 0.382153) 

So, it's better to use a hash when you are just retrieving some values (like in the example above). If there is additional logic to execute, a case-statement is still a way to go.