Performance-UnfreezeString.md

Pattern: Use of String#dup/String.new to unfreeze string

Issue: -

Description

In Ruby 2.3 or later, use unary plus operator to unfreeze a string literal instead of String#dup and String.new. Unary plus operator is faster than String#dup.

Note: String.new (without operator) is not exactly the same as +''. These differ in encoding. String.new.encoding is always ASCII-8BIT. However, (+'').encoding is the same as script encoding(e.g. UTF-8). So, if you expect ASCII-8BIT encoding, disable this rule.

Examples

# bad
''.dup
"something".dup
String.new
String.new('')
String.new('something')

# good
+'something'
+''

Further Reading

• RuboCop - Performance/UnfreezeString