Looking for an (elegant) solution for splitting a string and keeping the separator as item(s) in the array
example 1:
"hello world"
["hello", " ", "world"]
example 2:
" hello world"
[" ", "hello", " ", "world"]
thx.
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1What about this stackoverflow.com/q/32361412 ?Martin R– Martin R2019-02-25 16:13:18 +00:00Commented Feb 25, 2019 at 16:13
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@MartinR thx for the link. I searched for solutions, and havent found this one. the solution(s) of that question are inspiring, yet don't work with separators longer than one char. example 2 seems to not work as well.fetzig– fetzig2019-02-25 16:24:47 +00:00Commented Feb 25, 2019 at 16:24
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4 Answers
Suppose you are splitting the string by a separator called separator, you can do the following:
let result = yourString.components(separatedBy: separator) // first split
.flatMap { [$0, separator] } // add the separator after each split
.dropLast() // remove the last separator added
.filter { $0 != "" } // remove empty strings
For example:
let result = " Hello World ".components(separatedBy: " ").flatMap { [$0, " "] }.dropLast().filter { $0 != "" }
print(result) // [" ", "Hello", " ", "World", " "]
2 Comments
Alexander
@Sweeper I thought there was a version of
components(separatedBy:) that had an optional parameter to exclude empty results. Have you seen anything like that?
Sweeper
I know you can do that in C# but I don't think that exists in Swift. @Alexander
For people who have a condition for their split, for example: splitting a camelCaseString based on uppercase condition:
extension Sequence {
func splitIncludeDelimiter(whereSeparator shouldDelimit: (Element) throws -> Bool) rethrows -> [[Element]] {
try self.reduce([[]]) { group, next in
var group = group
if try shouldDelimit(next) {
group.append([next])
} else {
group[group.lastIdx].append(next)
}
return group
}
}
}
For example:
"iAmCamelCase".splitIncludeDelimiter(whereSeparator: \.isUppercase)
=>
["i", "Am", "Camel", "Case"]
(If you want the imp of isUppercase)
extension CharacterSet {
static let uppercaseLetters = CharacterSet(charactersIn: "ABCDEFGHIJKLMNOPQRSTUVWXYZ")
}
extension Unicode.Scalar {
var isUppercase: Bool {
CharacterSet.uppercaseLetters.contains(self)
}
}
1 Comment
marosoaie
Nice idea, but this doesn't compile. If you move the extension on RandomAccessCollection you do have an
endIndex which can be used instead of lastIdxJust for fun, the Swift Algorithms package contains an algorithm called Intersperse
After adding the package and
import Algorithms
you can write
let string = "hello world"
let separator = " "
let result = Array(string
.components(separatedBy: separator)
.interspersed(with: separator))
print(result)
Your second example is barely correct, the result of splitting " hello world" by space is
["", "hello", "world"]
Comments
let sample = "a\nb\n\nc\n\n\nd\n\nddddd\n \n \n \n\n"
let sep = "\n"
let result = sample.components(separatedBy: sep).flatMap {
$0 == "" ? [sep] : [$0, sep]
}.dropLast()
debugPrint(result) // ArraySlice(["a", "\n", "b", "\n", "\n", "c", "\n", "\n", "\n", "d", "\n", "\n", "ddddd", "\n", " ", "\n", " ", "\n", " ", "\n", "\n"])
