Skip to content
Related Articles

Related Articles

Improve Article
Save Article
Like Article

Ruby | MatchData Class

  • Last Updated : 22 Nov, 2021

In Ruby, all the pattern matching is done with the help of special variable $~. All the pattern matches will set the $~ to a MatchData that contains the information about the match. The MatchData objects are returned by the Regexp#match and Regexp.last_match methods. The MatchData objects enclosed all the result of the pattern match, results that are normally accessed by the special variables, i.e $&, $’, $`, $1, $2 etc
 

Instance Method

Here match is the object of the MatchData Class.

  • [] : It is known as Match Reference. In this MatchData is behaves like an array and may be accessed by using normal array indexing technique. In this match[0] is equivalent to special variable $& and it returns the entire matched string. match[1], match[2], match[3] and so on, return the match back reference value.
match[i]
match[start, length]
match[range]

Example:

Ruby




# Ruby program to illustrate
# use of []
 
# Using [] operator
a = /(.)(.)(\d+)(\d)/.match("GeeksFORgeeks12.")
a[0]
a[1, 4]
a[1..2]
a[-2, 1

Output: 



"ks12"
["k", "s", "1", "2"]
["k", "s"]
["1"]
  • begin : This method returns the offset of the start of the nth element of the match array in the string.
match.begin(n)

Example:

Ruby




# Ruby program to illustrate
# use of begin method
 
# Using begin method
a = /(.)(.)(\d+)(\d)/.match("GeeksFORgeeks112.")
a.begin(1)
a.begin(2)

Output: 

11
12
  • captures : This methods return the array of all the matching groups.
match.captures

Example:

Ruby




# Ruby program to illustrate
# use of captures method
 
# Using captures method
a = /(.)(.)(\d+)(\d)/.match("GeeksFORgeeks112.")
a.captures

Output: 

["k", "s", "11", "2"]
  • end : This method returns the offset into the character that immediately following the end of the nth element of thematch array in the string.
match.end(n)

Example:

Ruby






# Ruby program to illustrate
# use of end method
 
# Using end method
a = /(.)(.)(\d+)(\d)/.match("GeeksFORgeeks112.")
a.end(0)
a.end(2)

Output: 

16
13
  • length : This method returns the number of elements present in the match array.
match.length

Example:

Ruby




# Ruby program to illustrate
# use of length method
 
# Using length method
a = /(.)(.)(\d+)(\d)/.match("GeeksFORgeeks112.")
a.length
 
# using size method
a.size

Output: 

5
5
  • offset : This method return a two-element array that consist of starting and ending offset of the nth match.
match.offset(n)

Example:

Ruby




# Ruby program to illustrate
# use of offset method
 
# Using offset method
a = /(.)(.)(\d+)(\d)/.match("GeeksFORgeeks112.")
a.offset(2)
a.offset(1)

Output: 

[12, 13]
[11, 12]
  • post_match : This method returns the piece of the original string after the current match. Identical to the special variable $’.
match.post_match

Example: 

Ruby




# Ruby program to illustrate
# use of post_match method
 
# Using post_match method
a = /(.)(.)(\d+)(\d)/.match("GeeksFORgeeks112: Ruby")
a.post_match

Output: 



": Ruby"
  • pre_match : This method returns the piece of the original string before the currentmatch. Identical to the special variable $`.
match.pre_match

Example:

Ruby




# Ruby program to illustrate
# use of pre_match method
 
# Using pre_match method
a = /(.)(.)(\d+)(\d)/.match("GeeksFORgeeks112: Ruby")
a.pre_match

Output: 

"GeeksFORgee"
  • select : This method return an array that consist of all the elements of match for which the block is true.
match.select{|val|block}
  • size : This method is similar to MatchData#length method.
match.size
  • string : This method return a frozen copy of the string passed in the match.
match.string

Example:

Ruby




# Ruby program to illustrate
# use of string method
 
# Using string method
a = /(.)(.)(\d+)(\d)/.match("GeeksFORgeeks112: Ruby")
a.string

Output: 

"GeeksFORgeeks112: Ruby"
  • to_a : This method returns the array of matches.
match.to_a

Example:

Ruby




# Ruby program to illustrate
# use of to_a method
 
# Using to_a method
a = /(.)(.)(\d+)(\d)/.match("GeeksFORgeeks112: Ruby")
a.to_a

Output:

["ks112", "k", "s", "11", "2"]
  • to_s : This method returns the whole matched string.
match.to_s

Example: 

Ruby




# Ruby program to illustrate
# use of to_s method
 
# Using to_s method
a = /(.)(.)(\d+)(\d)/.match("GeeksFORgeeks112: Ruby")
a.to_s

Output: 

"ks112"
  • values_at : In this method index is used to access the matching values and return an array of corresponding match.
match.valu_at([index]*)

Example:

Ruby




# Ruby program to illustrate
# use of values_at method
 
# Using values_at method
a = /(.)(.)(\d+)(\d)/.match("GeeksFORgeeks112: Ruby")
a.values_at(2, 0)

Output:

["s", "ks112"]
  • == : It is known as Equality. It is used to check if both MatchData, i.e match1 and match2 are equal or not. If they are equal, then return true, otherwise return false. 
match1==match2

Reference: https://ruby-doc.org/core-2.2.0/MatchData.html




My Personal Notes arrow_drop_up
Recommended Articles
Page :

Start Your Coding Journey Now!