Converting a multi line string to an array in Ruby using line breaks as delimiters

I like to use this as a pretty generic method for handling newlines and returns:

lines = string.split(/\n+|\r+/).reject(&:empty?)

string = "P07091 MMCNEFFEG

P06870 IVGGWECEQHS

SP0A8M0 VVPVADVLQGR

P01019 VIHNESTCEQ"

Using CSV::parse

require 'csv'

CSV.parse(string).flatten
# => ["P07091 MMCNEFFEG", "P06870 IVGGWECEQHS", "SP0A8M0 VVPVADVLQGR", "P01019 VIHNESTCEQ"]

Another way using String#each_line :-

ar = []
string.each_line { |line| ar << line.strip unless line == "\n" }
ar # => ["P07091 MMCNEFFEG", "P06870 IVGGWECEQHS", "SP0A8M0 VVPVADVLQGR", "P01019 VIHNESTCEQ"]

Building off of @Martin's answer:

lines = string.split("\n").reject(&:blank?)

That'll give you only the lines that are valued

Split can take a parameter in the form of the character to use to split, so you can do:

lines = string.split("\n")

I think it should be noted that in some situations, line breaks can include not only newlines (\n) but also carriage returns (\r) and that there could potentially be any combination or quantity thereof. Let's take the following string for example:

str = "Useful Line 1  ....
  Useful Line 2
           
Useful Line 3
  Useful Line 4...                                           \n
Useful Line 5\r      \n
  Useful Line 6\n\r
Useful Line 7\n\r\n\r
  Useful Line 8       \r\n\r\n
Useful Line 9\r\r\r  Useful Line 10\n\n\n\n\nUseful Line 11        \r  Useful Line 12"

To deal with all instances of \n and \r, I would do the following to replace all instances of \r with \n using gsub, and then I would combine all consecutive instances of \n using squeeze(arg):

str.gsub("\r", "\n").squeeze("\n")

which would result in :

#=>
"Useful Line 1  ....
  Useful Line 2
           
Useful Line 3
  Useful Line 4...                                           
Useful Line 5
      
  Useful Line 6
Useful Line 7
  Useful Line 8       
Useful Line 9
  Useful Line 10
Useful Line 11        
  Useful Line 12"

...which brings me to our next issue. Sometimes those extra line breaks contain unwanted whitespace and not truly blank or empty lines. To deal with not only line breaks but also unwanted empty lines, I would add the each_line, reject, and strip method like so:

str.gsub("\r", "\n").squeeze("\n").each_line.reject{|x| x.strip == ""}.join 

which would result in the desired string:

#=>
Useful Line 1  ....
  Useful Line 2
Useful Line 3
  Useful Line 4...                                           
Useful Line 5
  Useful Line 6
Useful Line 7
  Useful Line 8       
Usefule Line 9
  Useful Line 10
Useful Line 11        
  Useful Line 12

Now more specifically to the OP, we could then simply use split("\n") to finish it all off (as was already mentioned by others):

str.gsub("\r", "\n").squeeze("\n").each_line.reject{|x| x.strip == ""}.join.split("\n")

or we could simply skip straight to the desired array by replacing each_line with map and leaving off the unnecessary join like so:

str.gsub("\r", "\n").squeeze("\n").split("\n").map.reject{|x| x.strip == ""}

both of which would result in:

#=>    
["Useful Line 1  ....", "  Useful Line 2", "Useful Line 3", "  Useful Line 4...                                           ", "Useful Line 5", "  Useful Line 6", "Useful Line 7", "  Useful Line 8       ", "Usefule Line 9", "  Useful Line 10", "Useful Line 11        ", "  Useful Line 12"]

NOTE: You may also want to strip off leading and trailing whitespace from each line in which case we could replace .join.split("\n") with .map(&:strip) like so:

str.gsub("\r", "\n").squeeze("\n").each_line.reject{|x| x.strip == ""}.map(&:strip)

or

str.gsub("\r", "\n").squeeze("\n").split("\n").map.reject{|x| x.strip == ""}.map(&:strip)

which would both result in:

#=>
["Useful Line 1  ....", "Useful Line 2", "Useful Line 3", "Useful Line 4...", "Useful Line 5", "Useful Line 6", "Useful Line 7", "Useful Line 8", "Usefule Line 9", "Useful Line 10", "Useful Line 11", "Useful Line 12"]