Question

Say I have many arrays of same size, with some elements, for example one of those could be:

arr = ['a', 'b', 'c', 'd']

I want to call a different function on each element, depending on its index, so I could do this:

arr.each_with_index do do |el, idx| 
  case idx
  when 0
    functionA el
  when 1
    functionB el
  # and so on..
  end
end

Is there any shorter way to do this? Something similar to assigning to variables:

a, b, c, d = arr

but I want to call functions, instead of doing assignment.

Answer 1

You could prepare an array of funcs and then zip the two together. Something like this:

# stabby lambdas instead of methods. Because methods aren't objects.
func_a = ->(el) { puts "1 for #{el}" }
func_b = ->(el) { puts "2 for #{el}" }
func_c = ->(el) { puts "3 for #{el}" }


arr = ['a', 'b', 'c', 'd']
funcs = [func_a, func_b, func_c, func_a] # reusing func_a

arr.zip(funcs) {|a, f| f.call(a) }

# >> 1 for a
# >> 2 for b
# >> 3 for c
# >> 1 for d

But my methods are methods, not lambdas…

Here’s a trick how to turn methods to proc objects, so that you can put them in array and call later. Be wary, though, that those calls are more expensive as compared to regular methods (shouldn’t matter, unless you’re already squeezing cycles out of your CPU)

def func_a el; puts "1 for #{el}"; end
def func_b el; puts "2 for #{el}"; end
def func_c el; puts "3 for #{el}"; end


arr = ['a', 'b', 'c', 'd']
funcs = [method(:func_a), method(:func_b), method(:func_c), method(:func_a)] # reusing func_a

arr.zip(funcs) {|a, f| f.call(a) }

# >> 1 for a
# >> 2 for b
# >> 3 for c
# >> 1 for d