Iterate over a deeply nested level of hashes in Ruby

Question

So I have a hash, and for each level of the hash, I want to store its key and value. The problem is, a value can be another hash array. Furthermore, that hash can contain ke

Answer 1

If you want to recursively edit the hash, you could do something like this:

# Iterates over a Hash recursively
def each_recursive(parent, &block)
  parent.each do |path, value|
    if value.kind_of? Hash
      each_recursive parent, &block
    elsif value.is_a? Array
      # @TODo something different for Array?
    else
      yield(parent, path, container_or_field)
    end
  end
end

And you can do something like:

hash = {...}
each_recursive(hash) do |parent, path, value|
  parent[path] = value.uppercase
end

Answer 2

I recomend to use #deep_locate of hashie gem https://www.rubydoc.info/github/intridea/hashie/Hashie/Extensions/DeepLocate#deep_locate-instance_method

little bit hacky always return false not to seeking

hash.extend(Hashie::Extensions::DeepLocate)
hash.deep_locate -> (key, value, object) do 
  # what you want to do here!
  # key: hash key
  # value: hash value
  # object: hash_object
  false # prevent to stop seeking
end

Answer 3

If I understand the goal, then you should be able to pass in the parent to your save method. For the top level, it will be nil. The following shows the idea where puts is used as a place holder for the "save".

def save_pair(parent, myHash)
  myHash.each {|key, value|
    value.is_a?(Hash) ? save_pair(key, value) :
            puts("parent=#{parent.nil? ? 'none':parent}, (#{key}, #{value})")
  }
end

Here is an example call to it:

hash = Hash.new
hash["key1"] = "value1"
hash["key2"] = "value2"
hash["key3"] = Hash.new
hash["key3"]["key4"] = "value4"
hash["key3"]["key5"] = "value5"
hash["key6"] = Hash.new
hash["key6"]["key7"] = "value7"
hash["key6"]["key8"] = Hash.new
hash["key6"]["key8"]["key9"] = "value9"

save_pair(nil, hash)

Answer 4

This should do for JSON well. Minor enhancements to Mark's code where it converts everything to uppercase in a given hash:

def capitalize_hash(myHash)
    myHash.each {|key, value|
        puts "isHash: #{value.is_a?(Hash)}: " + value.to_s
        value.is_a?(Hash) ? capitalize_hash(value) : ( value.is_a?(Array) ? (myHash[key] = capitalize_array(value)) : (myHash[key] = value.try(:upcase)))
    }
end

def capitalize_array(myArray)
    myArray.each {|value|
        puts "isHash: #{value.is_a?(Hash)}: " + value.to_s
        value.is_a?(Array) ? capitalize_array(value) : ( value.is_a?(Hash) ? capitalize_hash(value) : value.try(:upcase))
    }
end

Answer 5

Here is recursive (read improved) version of Hash::each(Hash::each_pair) with block and enumerator support:

module HashRecursive
    refine Hash do
        def each(recursive=false, &block)
            if recursive
                Enumerator.new do |yielder|
                    self.map do |key, value|
                        value.each(recursive=true).map{ |key_next, value_next| yielder << [[key, key_next].flatten, value_next] } if value.is_a?(Hash)
                        yielder << [[key], value]
                    end
                end.entries.each(&block)
            else
                super(&block)
            end
        end
        alias_method(:each_pair, :each)
    end
end

using HashRecursive

Here are usage examples of Hash::each with and without recursive flag:

hash = {
    :a => {
        :b => {
            :c => 1,
            :d => [2, 3, 4]
        },
        :e => 5
    },
    :f => 6
}

p hash.each, hash.each {}, hash.each.size
# #<Enumerator: {:a=>{:b=>{:c=>1, :d=>[2, 3, 4]}, :e=>5}, :f=>6}:each>
# {:a=>{:b=>{:c=>1, :d=>[2, 3, 4]}, :e=>5}, :f=>6}
# 2

p hash.each(true), hash.each(true) {}, hash.each(true).size
# #<Enumerator: [[[:a, :b, :c], 1], [[:a, :b, :d], [2, 3, 4]], [[:a, :b], {:c=>1, :d=>[2, 3, 4]}], [[:a, :e], 5], [[:a], {:b=>{:c=>1, :d=>[2, 3, 4]}, :e=>5}], [[:f], 6]]:each>
# [[[:a, :b, :c], 1], [[:a, :b, :d], [2, 3, 4]], [[:a, :b], {:c=>1, :d=>[2, 3, 4]}], [[:a, :e], 5], [[:a], {:b=>{:c=>1, :d=>[2, 3, 4]}, :e=>5}], [[:f], 6]]
# 6

hash.each do |key, value|
    puts "#{key} => #{value}"
end
# a => {:b=>{:c=>1, :d=>[2, 3, 4]}, :e=>5}
# f => 6

hash.each(true) do |key, value|
    puts "#{key} => #{value}"
end
# [:a, :b, :c] => 1
# [:a, :b, :d] => [2, 3, 4]
# [:a, :b] => {:c=>1, :d=>[2, 3, 4]}
# [:a, :e] => 5
# [:a] => {:b=>{:c=>1, :d=>[2, 3, 4]}, :e=>5}
# [:f] => 6

hash.each_pair(recursive=true) do |key, value|
    puts "#{key} => #{value}" unless value.is_a?(Hash)
end
# [:a, :b, :c] => 1
# [:a, :b, :d] => [2, 3, 4]
# [:a, :e] => 5
# [:f] => 6

Here is example from the question itself:

hash = {
    :key1   =>  'value1',
    :key2   =>  'value2',
    :key3   =>  {
        :key4   =>  'value4',
        :key5   =>  'value5'
    },
    :key6   =>  {
        :key7   =>  'value7',
        :key8   =>  {
            :key9   =>  'value9'
        }
    }
}

hash.each_pair(recursive=true) do |key, value|
    puts "#{key} => #{value}" unless value.is_a?(Hash)
end
# [:key1] => value1
# [:key2] => value2
# [:key3, :key4] => value4
# [:key3, :key5] => value5
# [:key6, :key7] => value7
# [:key6, :key8, :key9] => value9

Also take a look at my recursive version of Hash::merge(Hash::merge!) here.

Answer 6

I know this is a late reply, but I just implemented a non-recursive solution to your problem and thought it is worth sharing.

class Hash
  def deep_traverse(&block)
    stack = self.map{ |k,v| [ [k], v ] }
    while not stack.empty?
      key, value = stack.pop
      yield(key, value)
      if value.is_a? Hash
        value.each{ |k,v| stack.push [ key.dup << k, v ] }
      end
    end
  end
end

Then, coming back to your original problem, you can do:

h = {
  :key1 => 'value1',
  :key2 => 'value2',
  :key3 => {
     :key4 => 'value4',
     :key5 => 'value5'
  },
  :key6 => {
    :key7 => 'value7',
    :key8 => {
      :key9 => 'value9'
    }
  }
}
h.deep_traverse{ |path,value| p [ path, value ] }
# => [[:key6], {:key7=>"value7", :key8=>{:key9=>"value9"}}]
#    [[:key6, :key8], {:key9=>"value9"}]
#    [[:key6, :key8, :key9], "value9"]
#    [[:key6, :key7], "value7"]
#    [[:key3], {:key4=>"value4", :key5=>"value5"}]
#    [[:key3, :key5], "value5"]
#    [[:key3, :key4], "value4"]
#    [[:key2], "value2"]
#    [[:key1], "value1"]

There is also a gist version.