deep_blank.rb

def deep_blank?(hash)
  hash.each do |k,v|
    any_blank = v.is_a?(Hash) ? deep_blank?(v) : v.empty?
    return false if !any_blank || k == '_destroy'
  end
  return true
end

def deep_blank(hash)
  hashes = { hash: hash }
  keys = [:hash]
  while keys.size > 0 do
    key = Array(keys.shift)
    hash = key.inject(hashes, :fetch)
    hash.each do |k,v|
      if v.is_a?(Hash)
        keys << (key + [k])
      else
        return false unless v.empty?
      end
    end
  end
  return true
end

deep_hash = {
  a: '',
  b: '',
  c: { d: '', e: '' },
  f: { g: '', h: { j: '' } },
  k: { l: '', m: { n: { o: '' } } },
  p: { q: '', r: '', s: { t: { u: { w: ''} } } }
}

deep_hash_with_value = {
  a: '',
  b: '',
  c: { d: '', e: '' },
  f: { g: '', h: { j: '' } },
  k: { l: '', m: { n: { o: "some_passed_value" } } },
  p: { q: '', r: '', s: { t: { u: { w: ''} } } }
}


require 'benchmark/ips'

Benchmark.ips do |x|
  x.report("recursion") { deep_blank?(deep_hash) }
  x.report("stack") { deep_blank(deep_hash) }

  x.compare!
end

Benchmark.ips do |x|
  x.report("recursion with value") { deep_blank?(deep_hash_with_value) }
  x.report("stack with value") { deep_blank(deep_hash_with_value) }

  x.compare!
end

# 
# Warming up --------------------------------------
#            recursion    14.700k i/100ms
#                stack     6.990k i/100ms
# Calculating -------------------------------------
#            recursion    156.470k (± 4.0%) i/s -    793.800k in   5.081689s
#                stack     70.396k (± 8.3%) i/s -    349.500k in   5.004201s

# Comparison:
#            recursion:   156469.9 i/s
#                stack:    70396.3 i/s - 2.22x  slower

# Warming up --------------------------------------
# recursion with value    21.617k i/100ms
#     stack with value     8.396k i/100ms
# Calculating -------------------------------------
# recursion with value    226.315k (± 6.2%) i/s -      1.146M in   5.082810s
#     stack with value     88.074k (± 3.5%) i/s -    444.988k in   5.058501s

# Comparison:
# recursion with value:   226314.6 i/s
#     stack with value:    88073.7 i/s - 2.57x  slower
#