Gsub and gsub in ruby! Difference

Ruby contains "! "And no "! "The biggest difference between methods is that "! "Will change the calling object itself. For example, str. gsub (/A/, 'B') does not change STR itself, but only returns a new Str. Str. gsub! (/A/, 'B') will change the STR itself.

But gsub and gsub! Another difference is that gsub returns a new string regardless of the situation, while gsub! A new string is returned only when a character is replaced. If no character is replaced, gsub! Only NIL is returned.

Example:

'Abc'. gsub (/A/, 'B') # Return 'BBC'

'Abc'. gsub! (/A/, 'B') # Return 'BBC'

'Abc'. gsub (/D/, 'A') # Return 'abc'

'Abc'. gsub! (/D/, 'A') # Return Nil