module Nuggets::Hash::NestMixin

Creates a nested hash, depth levels deep, that yields arrays at the last level.

Example:

hash = Hash.array(2)
hash[:foo][:bar][:a] << 1 << 2
hash[:foo][:bar][:b] << 3 << 4
hash
#=> {:foo=>{:bar=>{:a=>[1, 2], :b=>[3, 4]}}}

    # File lib/nuggets/hash/nest_mixin.rb
102 def array(depth = 0)
103   nest(depth) { [] }
104 end

Creates a nested hash, depth levels deep, that yields the keys themselves at the last level.

Example:

hash = Hash.identity(2)
hash[:foo][:bar][:a] #=> :a
hash[:foo][:bar][:b] #=> :b
hash
#=> {:foo=>{:bar=>{:a=>:a, :b=>:b}}}

   # File lib/nuggets/hash/nest_mixin.rb
85 def identity(depth = 0)
86   nest(depth) { |key| key }
87 end

Creates a nested hash, depth levels deep. The final hash will receive a default value of value or, if value is not given but a block is given, the result of the key yielded to that block, or, otherwise, the hash's original default value, typically nil.

NOTE: If you set the default value for one of the nested hashes explicitly, all of the effects described here disappear for that hash because that also means that the default proc will be cleared.

Example:

hash = Hash.nest(2)
hash[:foo][:bar][:a] = { x: 1, y: 2 }
hash[:foo][:bar][:b] = { x: 0, y: 3 }
hash
#=> {:foo=>{:bar=>{:b=>{:y=>3, :x=>0}, :a=>{:y=>2, :x=>1}}}}

   # File lib/nuggets/hash/nest_mixin.rb
52 def nest(depth = 0, value = default = true, &block)
53   if depth.zero?
54     if default
55       if block_given?
56         new { |hash, key| hash[key] = block[key] }
57       else
58         new { |hash, key| hash[key] = hash.default }
59       end
60     else
61       new { |hash, key| hash[key] = value }
62     end
63   else
64     if default
65       new { |hash, key| hash[key] = nest(depth - 1, &block) }
66     else
67       new { |hash, key| hash[key] = nest(depth - 1, value) }
68     end
69   end
70 end