Ruby - quick way to extract number from string-CodePudding

As a beginner in Ruby, is there a quick to extract the first and second number from this string 5.16.0.0-15? In this case, I am looking 5 and 16. Thanks

CodePudding user response：

One way is to use the method String#match with the regular expression

rgx = /(\d )\.(\d )/

to construct a MatchData object. The regular expression captures the first two strings of digits, separated by a period. The method MatchData#captures is then use to extract the contents of capture groups 1 and 2 (strings) and save them to an array. Lastly, String#to_i is used to convert the strings in the array to integers:

"5.16.0.0-15".match(rgx).captures.map(&:to_i)
  #=> [5, 16]

We see that

m = "5.16.0.0-15".match(rgx)
  #=> #<MatchData "5.16" 1:"5" 2:"16">
a = m.captures
  #=> ["5", "16"]
a.map(&:to_i)
  #=> [5, 16]

a.map(&:to_i) can be thought of as shorthand for a.map { |s| s.to_i }.

We can express the regular expression in free-spacing mode to make it self-documenting:

/
(      # begin capture group 1
  \d   # match one or more digits
)      # end capture group 1
\.     # match a period
(      # begin capture group 2
  \d   # match one or more digits
)      # end capture group 2
/x     # invoke free-spacing regex definition mode

CodePudding user response：

Use #split, telling it to split on "." and only split into three parts, then access the first two.

irb(main):003:0> s = "5.16.0.0-15"
=> "5.16.0.0-15"
irb(main):004:0> s.split(".", 2)
=> ["5", "16"]

Optionally map to integers.

irb(main):005:0> s.split(".", 2).map(&:to_i)
=> [5, 16]