case insensitive splitting swift 4? - ios

Question

Trying to split values in swift, and it works, but it is cAsE sEnSiTiVe. Is there a way of splitting them in swift 4 ignoring case?
"Hello There!"
"hello there!"
I am currently using String.components(seperatedBy: "Th") but that does only split the second string, "hello there!". Is there a way to split them both?

Answer 1

You can write something like this:
import Foundation
let str1 = "Hello There!"
let str2 = "hello there!"
extension String {
func caseInsensitiveSplit(separator: String) -> [String] {
//Thanks for Carpsen90. Please see comments below.
if separator.isEmpty {
return [self] //generates the same output as `.components(separatedBy: "")`
}
let pattern = NSRegularExpression.escapedPattern(for: separator)
let regex = try! NSRegularExpression(pattern: pattern, options: .caseInsensitive)
let matches = regex.matches(in: self, options: [], range: NSRange(0..<self.utf16.count))
let ranges = (0..<matches.count+1).map { (i: Int)->NSRange in
let start = i == 0 ? 0 : matches[i-1].range.location + matches[i-1].range.length
let end = i == matches.count ? self.utf16.count: matches[i].range.location
return NSRange(location: start, length: end-start)
}
return ranges.map {String(self[Range($0, in: self)!])}
}
}
print( str1.caseInsensitiveSplit(separator: "th") ) //->["Hello ", "ere!"]
print( str2.caseInsensitiveSplit(separator: "th") ) //->["hello ", "ere!"]
But I wonder what you want to do with "hello " and "ere!".
(You lose case-info of the separator, if it matched with "th", "tH", "Th" or "TH".)
If you can explain what you really want to do, someone would show you a better solution for it.

Answer 2

Just for fun another version using NSRegularExpression but extending StringProtocol:
Swift 4 or later
extension StringProtocol {
func caseInsensitiveComponents<T>(separatedBy separator: T) -> [SubSequence] where T: StringProtocol, Index == String.Index {
var index = startIndex
return ((try? NSRegularExpression(pattern: NSRegularExpression.escapedPattern(for: String(separator)), options: .caseInsensitive))?.matches(in: String(self), range: NSRange(location: 0, length: utf16.count))
.compactMap {
guard let range = Range($0.range, in: String(self))
else { return nil }
defer { index = range.upperBound }
return self[index..<range.lowerBound]
} ?? []) + [self[index...]]
}
}
Playground testing
let str1 = "Hello There!"
let str2 = "hello there!"
str1.caseInsensitiveComponents(separatedBy: "Th") // ["Hello ", "ere!"]
str2.caseInsensitiveComponents(separatedBy: "Th") // ["Hello ", "ere!"]

Answer 3

An possible solution is to get the range of the separator with .caseInsensitive option and extract the substrings from its lower- and upperBound.
extension StringProtocol where Index == String.Index {
func caseInsensitiveComponents(separatedBy separator: String) -> [SubSequence]
{
var result = [SubSequence]()
var currentIndex = startIndex
while let separatorRange = self[currentIndex...].range(of: separator, options: .caseInsensitive) {
result.append(self[currentIndex..<separatorRange.lowerBound])
currentIndex = separatorRange.upperBound
}
return result + [self[currentIndex...]]
}
}

Answer 4

You could lower case the whole string first:
let s = "Hello There!".lowercased().components(separatedBy: "th")

Answer 5

Not sure if i understood what you are trying to achieve, but you can try this.
var str = "Hello There!"
var str2 = "hello there!"
override func viewDidLoad() {
super.viewDidLoad()
let split1 = str.lowercased().replacingOccurrences(of: "th", with: " ")
let split2 = str2.lowercased().replacingOccurrences(of: "th", with: " ")
print(split1) //hello ere!
print(split2) //hello ere!
}

Answer 6

If you want to filter for a list of items containing a certain keyword, split the strings is the wrong approach. All you need is a simple check whether that keyword appears in the item:
let queryStr = "th"
let items = [
"Hello There!",
"hello there!"
]
let filterdItems = items.filter {
return $0.range(of: queryStr, options: .caseInsensitive) != nil
}