How to Use Match in Ruby Regex: Syntax and Examples

In Ruby, you use match to check if a string fits a regex pattern. It returns a MatchData object if it matches or nil if it doesn't. You call it like string.match(/pattern/).

Syntax

The match method is called on a string and takes a regular expression as an argument. It returns a MatchData object if the regex matches part of the string, or nil if there is no match.

• string.match(/pattern/): Checks if pattern exists in string.
• MatchData: Contains details about the match, like matched text and groups.
• nil: Means no match was found.

ruby

result = "hello world".match(/world/)
puts result.class
puts result[0]

Output

MatchData
world

Example

This example shows how to use match to find a word in a string and access the matched text and capture groups.

ruby

text = "My phone number is 123-456-7890."
match_data = text.match(/(\d{3})-(\d{3})-(\d{4})/)

if match_data
  puts "Full match: #{match_data[0]}"
  puts "Area code: #{match_data[1]}"
  puts "Prefix: #{match_data[2]}"
  puts "Line number: #{match_data[3]}"
else
  puts "No match found."
end

Output

Full match: 123-456-7890
Area code: 123
Prefix: 456
Line number: 7890

Common Pitfalls

One common mistake is expecting match to return a boolean. It returns MatchData or nil, so you must check for nil before using the result. Another pitfall is forgetting to escape special characters in the regex.

ruby

text = "price is $5"

# Wrong: assuming match returns true/false
if text.match(/\$5/)
  puts "Found price"
else
  puts "Price not found"
end

# Right: escape $ to match literal dollar sign
if text.match(/\$5/)
  puts "Found price"
else
  puts "Price not found"
end

Output

Found price
Found price

Quick Reference

• string.match(/regex/): Returns MatchData or nil.
• Use match_data[0] for full match.
• Use match_data[n] for capture groups.
• Check for nil before accessing match data.
• Escape special characters like $, ., ? in regex.

Key Takeaways

Use string.match(/pattern/) to find regex matches in Ruby strings.

Always check if the result is nil before using match data.

Access the full match with match_data[0] and groups with match_data[n].

Escape special regex characters to match them literally.

Match returns MatchData, not a boolean true/false.