* Deep Merge Concat *.md

Deep Merge Concat

Can be useful for "inheritance" in YAML.

deep_merge_concat.rb

require "active_support"
require "active_support/core_ext/hash/deep_merge"

class Hash
  def deep_merge_concat(other, &block)
    self.deep_merge(other) do |key, this_val, other_val|
      other_val = this_val + other_val if (this_val.is_a?(::Array) && other_val.is_a?(::Array))

      block ? block.call(key, this_val, other_val) : other_val
    end
  end
end

h1 = {a:{b: [1, 2, 3], c: {d: 1}}}

h2 = {a:{b: [4, 5, 6], c: {d: 2}}}

h1.deep_merge_concat(h2)
# => {:a=>{:b=>[1, 2, 3, 4, 5, 6], :c=>{:d=>2}}}