Question

I am using Ruby 1.9.2 and the Ruby on Rails v3.2.2 gem. I would like to refactoring the following code to one line:

args ||= {}

@i_vars = {}
args.each { |key, opts| @i_vars[key] = IVar.new(key, opts, args.keys) }

I thought to use the inject method something like this:

args ||= {}

@ivars = args.inject({}) { |result, (key, opts)| result.merge( @i_vars[key] = IVar.new(key, opts, args.keys) ) }

However, the latter code returns different results when setting the @i_vars variable. I tried also others implementations of the inject method but without success.

There is a way to refactoring the code? or, maybe, should I use some other method or some RoR feature (unknown to me)?

Answer 1

What you should write in the inject block:

result.update(key => IVar.new(key, opts, args.keys)

But no need to use inject or each_with_object to build a hash, we have Hash[pairs]:

@i_vars = Hash[(args || {}).map { |k, opts| [k, IVar.new(k, opts, (args || {}).keys)] }

However, I wouldn’t obsess with one-liners, I’d write an equivalent but more clear code:

hargs = args || {}
@i_vars = Hash[hargs.map do |key, opts| 
  [key, IVar.new(key, opts, hargs.keys)]
end]