'subscript(_:)' is unavailable: cannot subscript String with an Int, use a String.Index instead in swift

This is my code:

let textRange = UETextRange(charIndex: i, length: l - i)
for j in textRange.charIndex...getCharIndexAfterEndOfRange(range: textRange) {   
    if String(initialText[j - 1]) == "\n" { //error here
        hits += 1
        let hitIndex = attributeRange.index + (hits - 1)
        if hitIndex <= paragraphStyles.count {
            let charIndex = paragraphStyles[hitIndex].charIndex
        }
    }
}

How do I solve this error?

>Solution :

Accessing elements of a String in Swift works slightly differently to most languages. Swift’s String subscript expects a String.Index (not an Int), as shown in the documentation:

@inlinable public subscript(i: String.Index) -> Character { get }

What we want to do instead is get the startIndex, offset that by the integer index we want, and then get that index from the string. Fixed code:

let char = initialText[initialText.index(initialText.startIndex, offsetBy: j - 1)]

if char == "\n" {
    /* ... */
}