Allows for reverse merging where its the keys in the calling hash that wins over those in the other_hash. This is particularly useful for initializing an incoming option hash with default values:

def setup(options = {})
  options.reverse_merge! :size => 25, :velocity => 10
end

The default :size and :velocity is only set if the options passed in doesn’t already have those keys set.

Methods
R
Instance Public methods
reverse_merge(other_hash)
Also aliased as: reverse_update

Source: show 

# File rails/activesupport/lib/active_support/core_ext/hash/reverse_merge.rb, line 13
def reverse_merge(other_hash)
  other_hash.merge(self)
end
reverse_merge!(other_hash)

Source: show 

# File rails/activesupport/lib/active_support/core_ext/hash/reverse_merge.rb, line 17
def reverse_merge!(other_hash)
  replace(reverse_merge(other_hash))
end
reverse_update(other_hash)