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?

Answer 1

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? && 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? && 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? && 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? && v != false
        self.delete(k)
      elsif v.is_a?(Hash)
        v.remove_blank_values!
      end
    end
  end
end

Other options:

• Replace v.blank? && v != false with v.nil? || v == "" to strictly remove empty strings and nil values
• Replace v.blank? && v != false with v.nil? to strictly remove nil values
• Etc.

EDITED 2017/03/15 to keep false values and present other options