CODEWITHSUNDEEP
ruby-on-railsrubyregex
James Jiang
James Jiang

Reputation: 2193

Get match groups values off Ruby regex

just a newbie to Ruby here:

Tried similar code today as below:

m = /(.*)xyz(.*)/.match("abcxyzdef")

subsequently ruby will set global variables $1 = “abc" and $2 = “def" but if code is like 

str1 = $1
str1.gsub!('a', '0')
str2 = $2

in this case, str2 will NOT be able to get value from match groups str2=nil, unless 

str1 = $1 
str2 = $2
str1.gsub!('a', '0')

so just curious what magic is behind this?

Thanks for your help!

Upvotes: 0

Views: 134

Answers (3)

Patrick Oscity
Patrick Oscity

Reputation: 54734

As @UriAgassi suggested, I would prefer to access the MatchData object returned by match because it is less cryptic than the $0, …, $9 global variables. However, I tend to like the block form of match better, because it makes it clear what regex the matches belong to.

/(.*)xyz(.*)/.match("abcxyzdef") do |m|
  str1, str2 = m.captures
  str1.gsub!('a', '0')
end

Upvotes: 0

Uri Agassi
Uri Agassi

Reputation: 37419

Of course, you can always use the match return value (you even assign it to m):

str1 = m[1]
# => "abc"
str1.gsub!('a', '0')
# => "0bc"
str2 = m[2]
# => "def"

Upvotes: 0

Jørgen R
Jørgen R

Reputation: 10806

gsub, like match uses the regex engine and thus overwrites the $1, $2 variables. If you want access to the data stored in those variables, you need to store them in a temporary variable before excecuting another regex method.

result = [$1, $2]

Upvotes: 4

Related Questions