Removing all empty elements from a hash YAML

Question

How would I go about removing all empty elements  empty list items  from a nested Hash or YAML file

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Could be done with facets library  a missing features from standard library   like that   require  hash compact  require  enumerable recursively  hash recursively    v  v compact      Works with any Enumerable  including Array  Hash    Look how recursively method is implemented

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You can use Hash reject to remove empty key value pairs from a ruby Hash     Remove empty strings   a   first   b      c   third    reject    key value  value empty        gt    a  gt  first    c  gt  third      Remove nil  a   first   b  nil  c   third   reject    k v  v nil         gt    a  gt  first    c  gt  third      Remove nil  amp  empty strings  a      b  nil  c   third   reject    k v  v nil     v empty         gt    c  gt  third

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Rails 4 1 added Hash compact and Hash compact  as a core extensions to Ruby s Hash class  You can use them like this   hash     a  true  b  false  c  nil   hash compact                             gt    a  true  b  false   hash                                     gt    a  true  b  false  c  nil   hash compact                              gt    a  true  b  false   hash                                     gt    a  true  b  false     c  nil   compact                       gt       Heads up  this implementation is not recursive  As a curiosity  they implemented it using  select instead of  delete if for performance reasons  See here for the benchmark   In case you want to backport it to your Rails 3 app     config initializers rails4 backports rb  class Hash     as implemented in Rails 4     File activesupport lib active support core ext hash compact rb  line 8   def compact     self select       value   value nil      end end

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works for both hashes and arrays  module Helpers   module RecursiveCompact     extend self      def recursive compact hash or array        p   proc do   args          v   args last         v delete if  amp p  if v respond to   delete if         v nil     v respond to    empty     amp  amp  v empty        end        hash or array delete if  amp p      end   end end   P S  based on someones answer  cant find  usage - Helpers  RecursiveCompact recursive compact something

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The recursive version of https   stackoverflow com a 14773555 1519240 works  but not with HashWithIndifferentAccess or other classes that are kind of Hash    Here is the version I am using   def recursive compact   inject     do  new hash   k v       if  v nil        new hash k    v kind of  Hash    v recursive compact   v     end     new hash   end end   kind of  Hash  will accept more classes that are like a Hash   You can also replace inject     by inject HashWithIndifferentAccess new  if you want to access the new hash using both symbol and string

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Ruby s Hash compact  Hash compact  and Hash delete if  do not work on nested nil  empty  and or blank  values  Note that the latter two methods are destructive  and that all nil      false     and    values are counted as blank    Hash compact and Hash compact  are only available in Rails  or Ruby version 2 4 0 and above   Here s a non-destructive solution that removes all empty arrays  hashes  strings and nil values  while keeping all false values    blank  can be replaced with nil  or empty  as needed    def remove blank values hash    hash each with object     do   k  v   new hash      unless v blank   amp  amp  v    false       v is a  Hash    new hash k    remove blank values v    new hash k    v     end   end end   A destructive version   def remove blank values  hash    hash each do  k  v      if v blank   amp  amp  v    false       hash delete k      elsif v is a  Hash        hash k    remove blank values  v      end   end end   Or  if you want to add both versions as instance methods on the Hash class   class Hash   def remove blank values     self each with object     do   k  v   new hash        unless v blank   amp  amp  v    false         v is a  Hash    new hash k    v remove blank values   new hash k    v       end     end   end    def remove blank values      self each pair do  k  v        if v blank   amp  amp  v    false         self delete k        elsif v is a  Hash          v remove blank values        end     end   end end   Other options    Replace v blank   amp  amp  v    false with v nil     v       to strictly remove empty strings and nil values Replace v blank   amp  amp  v    false with v nil  to strictly remove nil values Etc    EDITED 2017 03 15 to keep false values and present other options

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If you re using Ruby 2 4   you can call compact and compact   h     a  1  b  false  c  nil   h compact     gt    a  1  b  false     https   ruby-doc org core-2 4 0 Hash html method-i-compact-21

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I know this thread is a bit old but I came up with a better solution which supports Multidimensional hashes  It uses delete if  except its multidimensional and cleans out anything with a an empty value by default and if a block is passed it is passed down through it s children     Hash cleaner class Hash     def clean          self delete if do  key  val              if block given                  yield key val              else                   Prepeare the tests                 test1   val nil                  test2   val     0                 test3   val     false                 test4   val empty  if val respond to   empty                    test5   val strip empty  if val is a  String   amp  amp  val respond to   empty                       Were any of the tests true                 test1    test2    test3    test4    test5             end         end          self each do  key  val              if self key  is a  Hash   amp  amp  self key  respond to   clean                    if block given                      self key    self key  clean   amp Proc new                  else                     self key    self key  clean                  end             end         end          return self     end end

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compact blank  Rails 6 1   If you are using Rails  or a standalone ActiveSupport   starting from version 6 1  there is a compact blank method which removes blank values from hashes  It uses Object blank  under the hood for determining if an item is blank    a   quot  quot   b  1  c  nil  d      e  false  f  true   compact blank     gt    b  1  f  true    Here is a link to the docs and a link to the relative PR  A destructive variant is also available  See Hash compact blank    If you need to remove only nil values  please  consider using Ruby build-in Hash compact and Hash compact  methods    a  1  b  false  c  nil   compact     gt    a  1  b  false

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I made a deep compact method for this that recursively filters out nil records  and optionally  blank records as well    class Hash     Recursively filters out nil  or blank - e g     if exclude blank  true is passed as an option  records from a Hash   def deep compact options           inject     do  new hash   k v         result   options  exclude blank    v blank    v nil        if  result         new value   v is a  Hash    v deep compact options  presence   v         new hash k    new value if new value       end       new hash     end   end end

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You could add a compact method to Hash like this  class Hash   def compact     delete if    k  v  v nil      end end   or for a version that supports recursion  class Hash   def compact opts         inject     do  new hash   k v         if  v nil          new hash k    opts  recurse   amp  amp  v class    Hash   v compact opts    v       end       new hash     end   end end

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I believe it would be best to use a self recursive method   That way it goes as deep as is needed   This will delete the key value pair if the value is nil or an empty Hash   class Hash   def compact     delete if   k v  v is a  Hash    v compact empty    v nil      end end   Then using it will look like this   x     a  gt   b  gt 2   c  gt 3    d  gt nil   e  gt   f  gt nil    g  gt         gt    a  gt   b  gt 2   c  gt 3    d  gt nil   e  gt   f  gt nil    g  gt      x compact     gt    a  gt   b  gt 2   c  gt 3     To keep empty hashes you can simplify this to   class Hash   def compact     delete if   k v  v compact if v is a  Hash   v nil      end end

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In Simple one liner for deleting null values in Hash   rec hash each   key value  rec hash delete key  if value blank

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Deep deletion nil values from a hash       returns new instance of hash with deleted nil values   def self deep remove nil values hash      hash each with object     do   k  v   new hash        new hash k    deep remove nil values v  if v is a  Hash        new hash k    v unless v nil      end   end      rewrite current hash   def self deep remove nil values  hash      hash each do  k  v        deep remove nil values v  if v is a  Hash        hash delete k  if v nil      end   end

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Use hsh delete if  In your specific case  something like  hsh delete if    k  v  v empty

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class Hash      def compact     def  empty  val        case val       when Hash     then val compact empty        when Array    then val all     v   empty  v          when String   then val empty        when NilClass then true             custom checking        end     end      delete if     key  val   empty  val         end  end

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Here is something I have     recursively remove empty keys  hashes   values  array   hashes and arrays from hash or array def sanitize data   case data   when Array     data delete if    value  res   sanitize value   res blank      when Hash     data delete if       value  res   sanitize value   res blank      end   data blank    nil   data end

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This one would delete empty hashes too   swoop   Proc new    k  v  v delete if  amp swoop  if v kind of  Hash    v empty    hsh delete if  amp swoop

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our version   it also cleans the empty strings and nil values  class Hash    def compact     delete if  k  v          v is a  Hash  and v respond to   empty    and v compact empty   or            v nil    or            v is a  String  and v empty           end  end

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Try this to remove nil  hash     a  true  b  false  c  nil     gt    a  gt true   b  gt false   c  gt nil  hash inject      c   k  v   c k    v unless v nil   c    gt    a  gt true   b  gt false

[ruby-on-rails] Removing all empty elements from a hash / YAML?

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