How to use replacingOccurrences for NSAttributedString in swift?

Question

In a NSAttributed type statement, I want to keep the existing attributed value and give it a new attributed value.

The problem is that replacingOccurrences is only possible for string types, as I want to give a new value every time the word appears in the entire sentence.

If I change NSAttributedString to string type, the attributed value is deleted. I must keep the existing values.

How can I do that?

Answer 1

To get this working,

1. First you need to find the indices of all the duplicate substrings existing in a string. To get that you can use this: https://stackoverflow.com/a/40413665/5716829

extension String {
    func indicesOf(string: String) -> [Int] {
        var indices = [Int]()
        var searchStartIndex = self.startIndex

        while searchStartIndex < self.endIndex,
            let range = self.range(of: string, range: searchStartIndex..<self.endIndex),
            !range.isEmpty
        {
            let index = distance(from: self.startIndex, to: range.lowerBound)
            indices.append(index)
            searchStartIndex = range.upperBound
        }

        return indices
    }
}

2. Next you need to apply your desired attribute to substring at each index, i.e.

    let str = "The problem is that replacingOccurrences Hello is only possible for string types, as I want to give Hello a new value every time Hello the word appears in the entire sentence Hello."
    let indices = str.indicesOf(string: "Hello")
    let attrStr = NSMutableAttributedString(string: str, attributes: [.foregroundColor : UIColor.blue])
    for index in indices
    {
        //You can write your own logic to specify the color for each duplicate. I have used some hardcode indices
        var color: UIColor
        switch index
        {
        case 41:
            color = .orange
        case 100:
            color = .magenta
        case 129:
            color = .green
        default:
            color = .red
        }
        attrStr.addAttribute(.foregroundColor, value: color, range: NSRange(location: index, length: "Hello".count))
    }

Screenshot:

Let me know if you still face any issues. Happy Coding..🙂