Question

How can I transform a string into a regex string, properly escaping all regex-specific characters? I am using interpolation to build the regex string to allow users to customize the regex without having to touch the code (or expecting them to know regex)

Example

custom_text = "Hello"    
my_regex = /#{custom_text}:\s*(\d+)/i

Which results in the following regex when my code uses it

/Hello:\s*(\d+)/i

This allows users to perhaps provide language localizations without having to worry about figuring out where my regex is used, how it’s used, or whether they will break the script if they changed something.

However if they wanted to include things like periods or question marks like Hello?, I would probably need to escape them first.

Answer 1

Use Regexp.escape:

my_regex = /#{Regexp.escape(custom_text)}:\s*(\d+)/i

For example:

>> puts /#{Regexp.escape('Hello?')}/.inspect
/Hello\?/