Validating phone number in ruby

Question

What are the rules for validating a North American phone number? Also, is there a regex I can use? Is there a gem to do this?

Here are few rules I have

Answer 1

Try this

(?:\+?|\b)[0-9]{10}\b

Explanation

@"
(?:         # Match the regular expression below
               # Match either the regular expression below (attempting the next alternative only if this one fails)
      \+          # Match the character “+” literally
         ?           # Between zero and one times, as many times as possible, giving back as needed (greedy)
   |           # Or match regular expression number 2 below (the entire group fails if this one fails to match)
      \b          # Assert position at a word boundary
)
[0-9]       # Match a single character in the range between “0” and “9”
   {10}        # Exactly 10 times
\b          # Assert position at a word boundary
"