CODEWITHSUNDEEP
rubyregexescapinggsub
Ryan Levick
Ryan Levick

Reputation: 51

How to replace single quotes with escaped single quotes in ruby

I'm trying to replace single quotes (') with escaped single quotes (\') in a string in ruby 1.9.3 and 1.8.7.

The exact problem string is "Are you sure you want to delete '%@'". This string should become "Are you sure you want to delete \'%@\'"

Using .gsub!(/\'/,"\'") leads to the following string "Are you sure you want to %@'%@".

Any ideas on what's going on?

Upvotes: 3

Views: 7487

Answers (3)

marcus erronius
marcus erronius

Reputation: 3703

String#gsub in the form gsub(exp,replacement) has odd quirks affecting the replacement string which sometimes require lots of escaping slashes. Ruby users are frequently directed to use the block form instead:

str.gsub(/'/){ "\\'" }

If you want to do away with escaping altogether, consider using an alternate string literal form:

str.gsub(/'/){ %q(\') }

Once you get used to seeing these types of literals, using them to avoid escape sequences can make your code much more readable.

Upvotes: 8

Chowlett
Chowlett

Reputation: 46685

\' in a substitution replacement string means "The portion of the original string after the match". So str.gsub!(/\'/,"\\'") replaces the ' character with everything after it - which is what you've noticed.

You need to further escape the backslash in the replacement. .gsub(/'/,"\\\\'") works in my irb console:

irb(main):059:0> puts a.gsub(/'/,"\\\\'")
Are you sure you want to delete \'%@\'

Upvotes: 1

sawa
sawa

Reputation: 168269

You need to escape the backslash. What about this?

"Are you sure you want to delete '%@'".gsub(/(?=')/, "\\")
# => "Are you sure you want to delete \\'%@\\'"

The above should be what you want. Your expected result is wrong. There is no way to literally see a single backslash when it means literally a backslash.

Upvotes: 0

Related Questions