10

I have the following string

str="HelloWorld How areYou I AmFine"

I want this string into the following array

["Hello","World How are","You I Am", "Fine"]

I have been using the following regex, it splits correctly but it also omits the matching pattern, i also want to retain that pattern. What i get is

str.split(/[a-z][A-Z]/)
 => ["Hell", "orld How ar", "ou I A", "ine"]

It omitts the matching pattern.

Can any one help me out how to retain these characters as well in the resulting array

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3 Answers 3

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7

In Ruby 1.9 you can use positive lookahead and positive lookbehind (lookahead and lookbehind regex constructs are also called zero-width assertions). They match characters, but then give up the match and only return the result, thus you won't loose your border characters:

str.split /(?<=[a-z])(?=[A-Z])/
=> ["Hello", "World How are", "You I Am", "Fine"]

Ruby 1.8 does not support lookahead/lookbehind constructs. I recommend to use ruby 1.9 if possible.

If you are forced to use ruby 1.8.7, I think regex won't help you and the best solution I can think of is to build a simple state machine: iterate over each character in your original string and build first string until you encounter border condition. Then build second string etc.

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4 Comments

Thanks for the answer, but it gives me the following erro ruby-1.8.7-p302 > str="HelloWorld How areYou I AmFine" => "HelloWorld How areYou I AmFine" ruby-1.8.7-p302 > str.split /(?<=[a-z])(?=[A-Z])/ SyntaxError: compile error (irb):987: undefined (?...) sequence: /(?<=[a-z])(?=[A-Z])/ from (irb):987 from :0
So what would be the solution in 1.8? I have to use 1.8.7
I found the answer from one of my colleague, for 1.8.7, do the following. str.underscore.split(/_/).each do |s| s.capitalize! end
@alex-kliuchnikau you can do this 1.8 using #scan instead of #split. Then you don't need the lookbehind.
5

Three answers so far, each with a limitation: one is rails-only and breaks with underscore in original string, another is ruby 1.9 only, the third always has a potential error with its special character. I really liked the split on zero-width assertion answer from @Alex Kliuchnikau, but the OP needs ruby 1.8 which doesn't support lookbehind. There's an answer that uses only zero-width lookahead and works fine in 1.8 and 1.9 using String#scan instead of #split.

str.scan /.*?[a-z](?=[A-Z]|$)/
=> ["Hello", "World How are", "You I Am", "Fine"]
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1 Comment

+1 for the scan lookahead -- your solution is safer, faster, shorter, and better than mine. :)
-1

I think this will do the job for you

str.underscore.split(/_/).each do |s| 
s.capitalize! 
end
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5 Comments

Note for the future visitors: This will work for Rails and will not work for pure ruby code because underscore is a Rails-specific method.
Note for the future: This will work only if there aren't any underscores in the original text.
Note For Future: In my case, i have been using rails and the strings that i have been manipulating does not contains '_' but the concerns raised by @joelparkerhenderson and @Alex are absolutely valid and must be consider befor using underscore function. Thanks @joel and @Alex again.
@nadeem-yasin this answer you've accepted is not a nice one, suffering both special character bug and requiring rails library.
I agree with dbenhur; his scan lookahead is shorter, faster, and safer that this solution and than my proposed solutions. IMHO you should change to accept dbenhur's.

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