CODEWITHSUNDEEP
swiftstringrangeswift3
koen
koen

Reputation: 5729

Update a Range in Swift 3

I'm trying to search a String for regex using the following snippet (it's in an extension for String):

var range = self.startIndex..<self.endIndex

while range.lowerBound < range.upperBound {
    if let match = self.range(of: regex, options: .regularExpression, range: range, locale: nil) {

        print(match)
        range = ????? <============  this line, how do I update the range?
    }
}

It will correctly find the first occurance, but then I don't know how to change the range to the position of the match to search the remainder of the string.

Upvotes: 4

Views: 3022

Answers (1)

Martin R
Martin R

Reputation: 539815

lowerBound and upperBound are immutable properties of the range, so you have to create a new range, starting at match.upperBound.

Also the loop should terminate if no match is found. That can be achieved by moving the binding let match = ... into the where condition.

var range = self.startIndex..<self.endIndex
while range.lowerBound < range.upperBound,
    let match = self.range(of: regex, options: .regularExpression, range: range) {
        print(match) // the matching range
        print(self.substring(with: match)) // the matched string

        range = match.upperBound..<self.endIndex
}

This can still lead to an infinite loop if an empty string matches the pattern (e.g. for regex = "^"). This can be solved, but as an alternative, use NSRegularExpression to get a list of all matches (see for example Swift extract regex matches).

Upvotes: 6

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