Without using NSRegularExpression, How can I get all matches of my string regular expression? - regex

Question

Swift 3 introduced String.range(of:options). Then, with this function, is possible match a part of string without creating a NSRegularExpression object, for example:
let text = "it is need #match my both #hashtag!"
let match = text.range(of: "(?:^#|\\s#)[\\p{L}0-9_]*", options: .regularExpression)!
print(text[match]) // #math
But, is possible match both occurrences of the regexp (that is, #match and #hashtag), instead of only the first?

Answer 1

let text = "it is need #match my both #hashtag!"
// create an object to store the ranges found
var ranges: [Range<String.Index>] = []
// create an object to store your search position
var start = text.startIndex
// create a while loop to find your regex ranges
while let range = text.range(of: "(?:^#|\\s#)[\\p{L}0-9_]*", options: .regularExpression, range: start..<text.endIndex) {
// append your range found
ranges.append(range)
// and change the startIndex of your string search
start = range.lowerBound < range.upperBound ? range.upperBound : text.index(range.lowerBound, offsetBy: 1, limitedBy: text.endIndex) ?? text.endIndex
}
ranges.forEach({print(text[$0])})
This will print
#match
#hashtag
If you need to use it more than once in your code you should add this extension to your project:
extension StringProtocol {
func ranges<S: StringProtocol>(of string: S, options: String.CompareOptions = []) -> [Range<Index>] {
var result: [Range<Index>] = []
var start = startIndex
while start < endIndex,
let range = self[start...].range(of: string, options: options) {
result.append(range)
start = range.lowerBound < range.upperBound ?
range.upperBound : index(after: range.lowerBound)
}
return result
}
}
usage:
let text = "it is need #match my both #hashtag!"
let pattern = "(?<!\\S)#[\\p{L}0-9_]*"
let ranges = text.ranges(of: pattern, options: .regularExpression)
let matches = ranges.map{text[$0]}
print(matches) // ["#match", "#hashtag"]