The regular expression class. See Regular Expressions for details.
Returns the MatchData object for the last regular expression match performed in the current scope. This method call is identical to a $~ reference.
/(.)(.)/ =~ "ab" p Regexp.last_match # => #<MatchData:0x4599e58> p Regexp.last_match[0] # => "ab" p Regexp.last_match[1] # => "a" p Regexp.last_match[2] # => "b" p Regexp.last_match[3] # => nil
If the integer nth is 0, returns the matching string ($&). Otherwise, returns the substring matching the nth set of parentheses ($1, $2, ...). When there are no corresponding parentheses or no matches, returns nil.
/(.)(.)/ =~ "ab" p Regexp.last_match # => #<MatchData:0x4599e58> p Regexp.last_match(0) # => "ab" p Regexp.last_match(1) # => "a" p Regexp.last_match(2) # => "b" p Regexp.last_match(3) # => nil
Because Regexp.last_match, with no arguments, returns nil when the entire regular expression does not match, the format last_match[1] will throw a NameError exception. On the other hand, last_match(1) returns nil.
Matches the string string to a regular expression. If the argument is not a string or does not match, returns false; if it matches, returns true.
Matching information can be configured in the built-in variable $~.
If string is neither nil nor a String object, throws a TypeError exception.
Identical to self=~str, except that it does not return a MatchData object. If there is no match, returns nil.
When only the substring matching the regular expression is needed, use match(str) like this:
bar = /foo(.*)baz/.match("foobarbaz").to_a[1]
_, foo, bar, baz = */(foo)(bar)(baz)/.match("foobarbaz")
to_a takes failed matches into account.
Creates and returns a string expression for a regular expression. Preserves the meaning of the returned string even if the string is embedded in another regular expression.
re = /foo|bar|baz/i
p re.to_s # => "(?i-mx:foo|bar|baz)"
p /#{re}+/o # => /(?i-mx:foo|bar|baz)+/
However, some regular expressions with backreferences may not work as expected. This is because backreferences can only be specified by number at present.
re = /(foo|bar)\1/ # \1 is foo or bar
p /(baz)#{re}/ # \1 is baz
# => /(baz)(?-mix:(foo|bar)\1)/