Unicode Character Conversion - ios

Question

I am attempting to use the unicode character U+00AE in a UITextView. If I use the code \u{00AE} using the below:
textView.text = "THING AND STUFF TrademarkedThing\u{00AE}"
However, if I pull some text from another location (this is technically coming from an API call, but that shouldn't matter), and assign it to the textView, I do not get the unicode character:
var apiText = "TrademarkedThing\u{00AE}" //Pulled from API call as text and saved into text variable
textView.text = "THING AND STUFF " + apiText
So the in the code below, the first unicode character does not show, but the second does.
var apiText = "TrademarkedThing\u{00AE}" //Pulled from API call as text and saved into text variable
textView.text = "THING AND STUFF " + apiText + " \u{00AE}"
Why won't the unicode from that text show?

Answer 1

The Unicode conversion (from \u{...}) only happens for string literals. You can see the problem if you compare these two:
let t1 = "Thing\u{00AE}"
// Thing®
let t2 = "Thing\\u{00" + "AE}"
// Thing\u{00AE}
Since your string is coming from another source, it acts like the second one. The Swift language book has a section on Unicode characters in string literals.
If you want to interpret those Unicode sequences after the fact, here's a String extension:
extension String {
func indexOfSubstring(str: String, fromIndex: String.Index? = nil) -> String.Index? {
var index = fromIndex ?? startIndex
while index < endIndex {
if self[Range(start: index, end: endIndex)].hasPrefix(str) {
return index
}
index = index.successor()
}
return nil
}
func convertedUnicodeSequences() -> String {
if let index = indexOfSubstring("\\u{") {
if let nextIndex = indexOfSubstring("}", fromIndex: index) {
let substr = self[Range(start: advance(index, 3), end: nextIndex)]
let scalar = UnicodeScalar(UInt32(strtoul(substr, nil, 16)))
return self[Range(start: startIndex, end: index)] +
String(scalar) +
self[Range(start: nextIndex.successor(), end: endIndex)].convertedUnicodeSequences()
}
}
return self
}
}