Changing text based on the final letter of user name using regular expression

Question

I am looking to change the ending of the user name based on the use case (in the language system will operate, names ends depending on how it is used).

So need to defin

Answer 1

@Sundeep makes an important observation in a comment on the question. If, for example, the substitutions were give by the following hash:

g = {'e'=>'ai', 's'=>'es', 'us'=>'mi', 'i' => 'as'}
  #=> {"e"=>"ai", "s"=>"es", "us"=>"mi", "i"=>"as"}

'surnamus' would be converted (incorrectly) to 'surnamues' merely because 's'=>'es' precedes 'us'=>'mi' in g. That situation may not exist at present, but it may be prudent to allow for it in future, particularly because it is so simple to do so:

h = g.sort_by { |k,_| -k.size }.to_h
  #=> {"us"=>"mi", "e"=>"ai", "s"=>"es", "i"=>"as"}

arr = ['surname', 'surnamus', 'surnami', 'surnamo']

The substitutions can be done using the form of String@#sub that employs a hash as its second argument.

r = /#{Regexp.union(h.keys)}\z/
  #=> /(?-mix:us|e|s|i)\z/i
arr.map { |s| s.sub(r,h) }
  #=> ["surnamai", "surnammi", "surnamas", "surnamo"]

See also Regexp::union.

Incidentally, though key-insertion order has been guaranteed for hashes since Ruby v1.9, there is a continuing debate as to whether that property should be made use of in Ruby code, mainly because there was no concept of key order when hashes were first used in computer programs. This answer provides a good example of the benefit of exploiting key order.

Answer 2

You can use String#gsub with block. Docs say:

In the block form, the current match string is passed in as a parameter, and variables such as $1, $2, $`, $&, and $' will be set appropriately. The value returned by the block will be substituted for the match on each call.

So you can use a regex with concatenation of all substrings to be replaced and then replace it in the block, e.g. using a hash that maps matches to replacements.

Full example:

replacements = {'e'=>'ai', 'us'=>'mi', 'i' => 'as'}
['surname', 'surnamus', 'surnami'].map do |s| 
  s.gsub(/(e|us|i)$/){|p| replacements[p] }
end