hash_subtraction is a gem that provides methods for different subtractive methods for hashes.

In your Gemfile:

gem 'hash_subtraction'

Then run bundle install.

to make use of hash_subtraction you must first extend the hash instance you wish to call the methods on.

myhash = {
  a: 'a', 
  b: 'b',
	num: 5,
	array: [1,2,3]
}
myhash2 = {
  a: 'a', 
  b: 'c',
	num: 10,
	array: [1,3]
}
#extend the hash
myhash.extend(HashSubtraction)

#subtract the hash
myhash-myhash2
#=> {:b=>"b", :num=>-5, :array=>[2]}
#arrays and numbers are subtracted, strings are removed if the value is a duplicate. Otherwise it is left alone.

#remove duplicate key value pairs
myhash.remove_duplicates(myhash2)
#=> {:b=>"b", :num=>5, :array=>[1, 2, 3]}
#only duplicate key and value combinations are removed

#remove duplicate keys
myhash.remove_duplicate_keys(myhash2)
#=> {}
#all matching keys are removed

#find the difference between the 2 hashes
myhash.diff(myhash2)
#=> {:b=>"c", :num=>10, :array=>[1, 3]}
# myhash[:a] is the only key value thats the same so it is excluded.
# The values from myhash2 will be listed if they are different as well as any keys in myhash1 not in myhash2

Copyright © 2014 Kelly Mahan, released under the MIT license