How to call different methods as given in an array

Question

Especially when working with structs, it would be nice to be able to call a different method per each element in an array, something like this:

array = %w{name 4 tag 0.343}
array.convert(:to_s, :to_i, :to_sym, :to_f)
# => ["name", 4, :tag, 0.343]

Are there any simple one-liners, ActiveSupport methods, etc. to do this easily?

Answer 1

I would do this:

class Array
  def convert(*args) map { |s| s.public_send args.shift } end
end    

array = %w{name 4 tag 0.343}
args = [:to_s, :to_i, :to_sym, :to_f]
array.convert(*args)
  #=> ["name", 4, :tag, 0.343]
args
  #=> [:to_s, :to_i, :to_sym, :to_f]

I included the last line to show that convert leaves args unchanged, even though args is emptied within convert. That's because args was splatted before being passed to convert.

As per @Arup's request, I've benchmarked his and my solutions:

class Array
  def sq_convert(*args)
    zip(args).map { |string, meth| string.public_send(meth) }
  end
  def lf_convert(*args)
    map { |s| s.public_send args.shift }
  end
end    

require 'benchmark'

n = 1_000_000
array = %w{name 4 tag 0.343}
args = [:to_s, :to_i, :to_sym, :to_f]

Benchmark.bmbm(15) do |x|
  x.report("Arup's super-quick   :") { n.times { array.sq_convert(*args) } }
  x.report("Cary's lightning-fast:") { n.times { array.lf_convert(*args) } }
end

# Rehearsal ----------------------------------------------------------
# Arup's super-quick   :   2.910000   0.000000   2.910000 (  2.922525)
# Cary's lightning-fast:   2.150000   0.010000   2.160000 (  2.155886)
# ------------------------------------------------- total: 5.070000sec

#                             user     system      total        real
# Arup's super-quick   :   2.780000   0.000000   2.780000 (  2.784528)
# Cary's lightning-fast:   2.090000   0.010000   2.100000 (  2.099337)