The regular expression class. See Regular Expression Literals for more information.
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 set 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)/