What is the best way to check if a string contains a substring in Ruby?

General Discussions
1

What is the best way to check if a string contains a substring in Ruby?

I have a string variable with the following content:

varMessage =   
  "hi/thsid/sdfhsjdf/dfjsd/sdjfsdn\n"
  "/my/name/is/balaji.so\n"
  "call::myFunction(int const&)\n"
  "void::secondFunction(char const&)\n"
  .
  .
  .
  "this/is/last/line/liobrary.so"

I need to check if a specific substring, such as:

"hi/thsid/sdfhsjdf/dfjsd/sdjfsdn\n"
"/my/name/is/balaji.so\n"
"call::myFunction(int const&)\n"

is present in varMessage. What is the best approach to determine whether a Ruby string contains a given substring?

2

If you just need a straightforward way to check if a substring exists within a string, include? is the easiest method.

if varMessage.include?("balaji.so")
  puts "Substring found!"
else
  puts "Substring not found."
end

It returns true if the substring is found and false otherwise. Simple and readable!

3

Have you tried using match? for a More Efficient Check : works well, but if you’re dealing with complex patterns, regular expressions (Regexp) can be more powerful. Instead of include?, you can use match?, which is optimized for checking matches without creating unnecessary objects.

if varMessage.match?(/balaji\.so/)
  puts "Substring found!"
end

This approach works well if you’re dealing with variations in the substring, like ignoring case or using regex patterns.

if varMessage.match?(/balaji\.so/i) # Case-insensitive check
  puts "Found!"
end

Plus, since match? doesn’t create a MatchData object, it’s slightly faster than using =~ or match when you just need a boolean result.

4

Those are great solutions, but what if you want to find all occurrences of a substring? That’s where scan comes in!

matches = varMessage.scan(/balaji\.so/)
puts "Found #{matches.count} occurrences." if matches.any?

Or, if you’re checking multiple lines of a file stored in an array, grep is useful.

lines = varMessage.split("\n")
matches = lines.grep(/balaji\.so/)
puts "Matched lines: #{matches}"

This is great for cases where you need to filter out only the lines containing a specific substring.