Ruby - quick way to extract number from string [closed] - ruby

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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

Answer 1

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
One reason for using a regular expression here is to confirm the structure of the string, should that be desired. That could be done by using the following regex:
rgx1 =
/
\A # match the beginning of the string
( # 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
(?: # begin a non-capture group
\. # match a period
\d+ # match one or more digits
(?: # begin a non-capture group
\- # match a hyphen
\d+ # match one or more digits
)? # end non-capture group and make it optional
)* # end non-capture group and execute it zero or more times
\z # match the end of the string
/x # invoke free-spacing regex definition mode
"5.16.0.0-15".match(rgx1).captures.map(&:to_i)
#=> [5, 16]
"5.16.0.A".match(rgx1)
#=> nil
"5.16.0.0-1-5".match(rgx1)
#=> nil
The last two examples would generate exceptions because nil has no method captures. One could of course handle those exceptions.
rgx1 is conventionally written /\A(\d+)\.(\d+)(x?:\.\d+(?:\-\d+)?)*\z/.

Answer 2

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(".", 3)[0..1]
=> ["5", "16"]
Optionally map to integers.
irb(main):005:0> s.split(".", 3)[0..1].map(&:to_i)
=> [5, 16]