function_strong_params.rb

#inspired by http://blog.martinosis.com/blog/simple-functional-strong-params-in-ruby/

require 'pp'

filter_hash = -> keys, params {
	keys.map { |key| [key, params[key]] }.to_h
}.curry

params = { name: 'Ion', age: 42, pwd: 'plain', contact: { address: 'Danil Ionescu' } }

pp filter_hash.([:name, :age]).(params)

hash_of = -> (fields, hash) {
	hash ||= {}
	fields.map { |key, fn| [key, fn.(hash[key])] }.to_h
}.curry

same = -> a { a }
contact = hash_of.(address: same)
user = hash_of.(name: same, 
	age: same,
	contact: contact)
pp user.(params)

array_of = -> fn, value { value.kind_of?(Array) ? value.map(&fn) : [] }.curry
contact_params = [{ address: '21 Jump Street', remove: 'me' }, { address: '24 Sussex', remove: 'me too' }, { address: '' }]
pp array_of.(contact).(contact_params)

default = -> default, a { a.empty? ? default : a }.curry

contact = hash_of.(address: default.('N/A'))
pp array_of.(contact).(contact_params)

scalar = -> a { a.kind_of?(Array) || a.kind_of?(Hash) ? nil : a }

pp hash_of.(name: scalar).(name: { hack: 'something' })
pp hash_of.(name: scalar).(name: 'Ion')