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Class: MatchData

Relationships & Source Files
Inherits: Object
Defined in: re.c,
re.c

Overview

MatchData is the type of the special variable $~, and is the type of the object returned by Regexp#match and Regexp.last_match. It encapsulates all the results of a pattern match, results normally accessed through the special variables $&, $', $`, $1, $2, and so on.

Instance Method Summary

Instance Method Details

#==(mtch2) ⇒ Boolean #eql?(mtch2) ⇒ Boolean
Also known as: #eql?

Equality—Two matchdata are equal if their target strings, patterns, and matched positions are identical.

#[](i) ⇒ String? #[](start, length) ⇒ Array #[](range) ⇒ Array #[](name) ⇒ String?

Match Reference – MatchData acts as an array, and may be accessed using the normal array indexing techniques. mtch[0] is equivalent to the special variable $&, and returns the entire matched string. mtch[1], mtch[2], and so on return the values of the matched backreferences (portions of the pattern between parentheses).

m = /(.)(.)(\d+)(\d)/.match("THX1138.")
m          #=> #<MatchData "HX1138" 1:"H" 2:"X" 3:"113" 4:"8">
m[0]       #=> "HX1138"
m[1, 2]    #=> ["H", "X"]
m[1..3]    #=> ["H", "X", "113"]
m[-3, 2]   #=> ["X", "113"]

m = /(?<foo>a+)b/.match("ccaaab")
m          #=> #<MatchData "aaab" foo:"aaa">
m["foo"]   #=> "aaa"
m[:foo]    #=> "aaa"

#begin(n) ⇒ Integer

Returns the offset of the start of the nth element of the match array in the string. n can be a string or symbol to reference a named capture.

m = /(.)(.)(\d+)(\d)/.match("THX1138.")
m.begin(0)       #=> 1
m.begin(2)       #=> 2

m = /(?<foo>.)(.)(?<bar>.)/.match("hoge")
p m.begin(:foo)  #=> 0
p m.begin(:bar)  #=> 2

#captures ⇒ Array

Returns the array of captures; equivalent to mtch.to_a[1..-1].

f1,f2,f3,f4 = /(.)(.)(\d+)(\d)/.match("THX1138.").captures
f1    #=> "H"
f2    #=> "X"
f3    #=> "113"
f4    #=> "8"

#end(n) ⇒ Integer

Returns the offset of the character immediately following the end of the nth element of the match array in the string. n can be a string or symbol to reference a named capture.

m = /(.)(.)(\d+)(\d)/.match("THX1138.")
m.end(0)         #=> 7
m.end(2)         #=> 3

m = /(?<foo>.)(.)(?<bar>.)/.match("hoge")
p m.end(:foo)    #=> 1
p m.end(:bar)    #=> 3

#==(mtch2) ⇒ Boolean #eql?(mtch2) ⇒ Boolean

Alias for #==.

#hash ⇒ Integer

Produce a hash based on the target string, regexp and matched positions of this matchdata.

See also Object#hash.

#inspect ⇒ String

Returns a printable version of mtch.

puts /.$/.match("foo").inspect
#=> #<MatchData "o">

puts /(.)(.)(.)/.match("foo").inspect
#=> #<MatchData "foo" 1:"f" 2:"o" 3:"o">

puts /(.)(.)?(.)/.match("fo").inspect
#=> #<MatchData "fo" 1:"f" 2:nil 3:"o">

puts /(?<foo>.)(?<bar>.)(?<baz>.)/.match("hoge").inspect
#=> #<MatchData "hog" foo:"h" bar:"o" baz:"g">

#length ⇒ Integer #size ⇒ Integer
Also known as: #size

Returns the number of elements in the match array.

m = /(.)(.)(\d+)(\d)/.match("THX1138.")
m.length   #=> 5
m.size     #=> 5

#names ⇒ Array, ...

Returns a list of names of captures as an array of strings. It is same as mtch.regexp.names.

/(?<foo>.)(?<bar>.)(?<baz>.)/.match("hoge").names
#=> ["foo", "bar", "baz"]

m = /(?<x>.)(?<y>.)?/.match("a") #=> #<MatchData "a" x:"a" y:nil>
m.names                          #=> ["x", "y"]

#offset(n) ⇒ Array

Returns a two-element array containing the beginning and ending offsets of the nth match. n can be a string or symbol to reference a named capture.

m = /(.)(.)(\d+)(\d)/.match("THX1138.")
m.offset(0)      #=> [1, 7]
m.offset(4)      #=> [6, 7]

m = /(?<foo>.)(.)(?<bar>.)/.match("hoge")
p m.offset(:foo) #=> [0, 1]
p m.offset(:bar) #=> [2, 3]

#post_match ⇒ String

Returns the portion of the original string after the current match. Equivalent to the special variable $'.

m = /(.)(.)(\d+)(\d)/.match("THX1138: The Movie")
m.post_match   #=> ": The Movie"

#pre_match ⇒ String

Returns the portion of the original string before the current match. Equivalent to the special variable $`.

m = /(.)(.)(\d+)(\d)/.match("THX1138.")
m.pre_match   #=> "T"

#regexp ⇒ Regexp

Returns the regexp.

m = /a.*b/.match("abc")
m.regexp #=> /a.*b/

#length ⇒ Integer #size ⇒ Integer

Alias for #length.

#string ⇒ String

Returns a frozen copy of the string passed in to match.

m = /(.)(.)(\d+)(\d)/.match("THX1138.")
m.string   #=> "THX1138."

#to_a ⇒ Array

Returns the array of matches.

m = /(.)(.)(\d+)(\d)/.match("THX1138.")
m.to_a   #=> ["HX1138", "H", "X", "113", "8"]

Because to_a is called when expanding *variable, there's a useful assignment shortcut for extracting matched fields. This is slightly slower than accessing the fields directly (as an intermediate array is generated).

all,f1,f2,f3 = * /(.)(.)(\d+)(\d)/.match("THX1138.")
all   #=> "HX1138"
f1    #=> "H"
f2    #=> "X"
f3    #=> "113"

#to_s ⇒ String

Returns the entire matched string.

m = /(.)(.)(\d+)(\d)/.match("THX1138.")
m.to_s   #=> "HX1138"

#values_at([index]*) ⇒ Array

Uses each index to access the matching values, returning an array of the corresponding matches.

m = /(.)(.)(\d+)(\d)/.match("THX1138: The Movie")
m.to_a               #=> ["HX1138", "H", "X", "113", "8"]
m.values_at(0, 2, -2)   #=> ["HX1138", "X", "113"]