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Crystal

MatchData

struct `Regex::MatchData`
inherits `Struct` ¶

Regex::MatchData is the type of the special variable $~, and is the type returned by Regex#match and String#match. It encapsulates all the results of a regular expression match.

if md = "Crystal".match(/[p-s]/)
  md.string # => "Crystal"
  md[0]     # => "r"
  md[1]?    # => nil
end

Many Regex::MatchData methods deal with capture groups, and accept an integer argument to select the desired capture group. Capture groups are numbered starting from 1, so that 0 can be used to refer to the entire regular expression without needing to capture it explicitly.

Methods¶

`#==(other : Regex::MatchData)` ¶

`#[](group_name : String)` ¶

Returns the match of the capture group named by group_name, or raises an KeyError if there is no such named capture group.

"Crystal".match(/r(?<ok>ys)/).not_nil!["ok"] # => "ys"
"Crystal".match(/r(?<ok>ys)/).not_nil!["ng"] # raises KeyError

When there are capture groups having same name, it returns the last matched capture group.

"Crystal".match(/(?<ok>Cr).*(?<ok>al)/).not_nil!["ok"] # => "al"

`#[](range : Range)` ¶

Returns all matches that are within the given range.

`#[](n : Int)` ¶

Returns the match of the nth capture group, or raises an IndexError if there is no nth capture group.

"Crystal".match(/r(ys)/).not_nil![1] # => "ys"
"Crystal".match(/r(ys)/).not_nil![2] # raises IndexError

`#[](start : Int, count : Int)` ¶

Returns count or less (if there aren't enough) matches starting at the given start index.

`#[]?(range : Range)` ¶

Like #[Range], but returns nil if the range's start is out of range.

`#[]?(group_name : String)` ¶

Returns the match of the capture group named by group_name, or nil if there is no such named capture group.

"Crystal".match(/r(?<ok>ys)/).not_nil!["ok"]? # => "ys"
"Crystal".match(/r(?<ok>ys)/).not_nil!["ng"]? # => nil

When there are capture groups having same name, it returns the last matched capture group.

"Crystal".match(/(?<ok>Cr).*(?<ok>al)/).not_nil!["ok"]? # => "al"

`#[]?(n : Int)` ¶

Returns the match of the nth capture group, or nil if there isn't an nth capture group.

When n is 0, returns the match for the entire Regex.

"Crystal".match(/r(ys)/).not_nil![0]? # => "rys"
"Crystal".match(/r(ys)/).not_nil![1]? # => "ys"
"Crystal".match(/r(ys)/).not_nil![2]? # => nil

`#[]?(start : Int, count : Int)` ¶

Like #[Int, Int] but returns nil if the start index is out of range.

`#begin(n = 0) : Int32` ¶

Returns the position of the first character of the nth match.

When n is 0 or not given, uses the match of the entire Regex. Otherwise, uses the match of the nth capture group.

"Crystal".match(/r/).not_nil!.begin(0)     # => 1
"Crystal".match(/r(ys)/).not_nil!.begin(1) # => 2
"クリスタル".match(/リ(ス)/).not_nil!.begin(0)    # => 1

`#byte_begin(n = 0)` ¶

Returns the position of the first byte of the nth match.

When n is 0 or not given, uses the match of the entire Regex. Otherwise, uses the match of the nth capture group.

"Crystal".match(/r/).not_nil!.byte_begin(0)     # => 1
"Crystal".match(/r(ys)/).not_nil!.byte_begin(1) # => 2
"クリスタル".match(/リ(ス)/).not_nil!.byte_begin(0)    # => 3

`#byte_end(n = 0)` ¶

Returns the position of the next byte after the match.

When n is 0 or not given, uses the match of the entire Regex. Otherwise, uses the match of the nth capture group.

"Crystal".match(/r/).not_nil!.byte_end(0)     # => 2
"Crystal".match(/r(ys)/).not_nil!.byte_end(1) # => 4
"クリスタル".match(/リ(ス)/).not_nil!.byte_end(0)    # => 9

`#captures` ¶

Returns an array of unnamed capture groups.

It is a difference from to_a that the result array does not contain the match for the entire Regex (self[0]).

match = "Crystal".match(/(Cr)(?<name1>y)(st)(?<name2>al)/).not_nil!
match.captures # => ["Cr", "st"]

# When this regex has an optional group, result array may contain
# a `nil` if this group is not matched.
match = "Crystal".match(/(Cr)(stal)?/).not_nil!
match.captures # => ["Cr", nil]

`#clone` ¶

`#dup` ¶

Returns a shallow copy of this object.

Because Value is a value type, this method returns self, which already involves a shallow copy of this object because value types are passed by value.

`#end(n = 0) : Int32` ¶

Returns the position of the next character after the match.

When n is 0 or not given, uses the match of the entire Regex. Otherwise, uses the match of the nth capture group.

"Crystal".match(/r/).not_nil!.end(0)     # => 2
"Crystal".match(/r(ys)/).not_nil!.end(1) # => 4
"クリスタル".match(/リ(ス)/).not_nil!.end(0)    # => 3

`#group_size : Int32` ¶

Returns the number of capture groups, including named capture groups.

"Crystal".match(/[p-s]/).not_nil!.group_size          # => 0
"Crystal".match(/r(ys)/).not_nil!.group_size          # => 1
"Crystal".match(/r(ys)(?<ok>ta)/).not_nil!.group_size # => 2

`#hash(hasher)` ¶

See Object#hash(hasher)

`#inspect(io : IO) : Nil` ¶

Appends this struct's name and instance variables names and values to the given IO.

struct Point
  def initialize(@x : Int32, @y : Int32)
  end
end

p1 = Point.new 1, 2
p1.to_s    # "Point(@x=1, @y=2)"
p1.inspect # "Point(@x=1, @y=2)"

`#named_captures` ¶

Returns a hash of named capture groups.

match = "Crystal".match(/(Cr)(?<name1>y)(st)(?<name2>al)/).not_nil!
match.named_captures # => {"name1" => "y", "name2" => "al"}

# When this regex has an optional group, result hash may contain
# a `nil` if this group is not matched.
match = "Crystal".match(/(?<name1>Cr)(?<name2>stal)?/).not_nil!
match.named_captures # => {"name1" => "Cr", "name2" => nil}

`#post_match` ¶

Returns the part of the original string after the match. If the match ends at the end of the string, returns the empty string.

"Crystal".match(/yst/).not_nil!.post_match # => "al"

`#pre_match` ¶

Returns the part of the original string before the match. If the match starts at the start of the string, returns the empty string.

"Crystal".match(/yst/).not_nil!.pre_match # => "Cr"

`#pretty_print(pp) : Nil` ¶

`#regex : Regex` ¶

Returns the original regular expression.

"Crystal".match(/[p-s]/).not_nil!.regex # => /[p-s]/

`#size` ¶

Returns the number of elements in this match object.

"Crystal".match(/[p-s]/).not_nil!.size          # => 1
"Crystal".match(/r(ys)/).not_nil!.size          # => 2
"Crystal".match(/r(ys)(?<ok>ta)/).not_nil!.size # => 3

`#string : String` ¶

Returns the original string.

"Crystal".match(/[p-s]/).not_nil!.string # => "Crystal"

`#to_a` ¶

Convert this match data into an array.

match = "Crystal".match(/(Cr)(?<name1>y)(st)(?<name2>al)/).not_nil!
match.to_a # => ["Crystal", "Cr", "y", "st", "al"]

# When this regex has an optional group, result array may contain
# a `nil` if this group is not matched.
match = "Crystal".match(/(Cr)(?<name1>stal)?/).not_nil!
match.to_a # => ["Cr", "Cr", nil]

`#to_h` ¶

Convert this match data into a hash.

match = "Crystal".match(/(Cr)(?<name1>y)(st)(?<name2>al)/).not_nil!
match.to_h # => {0 => "Crystal", 1 => "Cr", "name1" => "y", 3 => "st", "name2" => "al"}

# When this regex has an optional group, result array may contain
# a `nil` if this group is not matched.
match = "Crystal".match(/(Cr)(?<name1>stal)?/).not_nil!
match.to_h # => {0 => "Cr", 1 => "Cr", "name1" => nil}

`#to_s(io : IO) : Nil` ¶

Same as #inspect(io).