How to display indirectly given unicode character in Swift? - json

Question

In a JSON data file, I have a unicode character like this:
{
”myUnicodeCharacter”: ”\\u{25a1}”
}
I know how to read data from JSON files. The problem occurs when it contains characters which are represented as above.
I read it in to a String variable, myUnicodeCharacterString, which gets the value ”\u{25a1}”. I couldn't by the way use a single slash in the JSON data file because in such case it doesn't recognize the data in the file to be a proper JSON object, returning nil.
However, the value is not encoded to its graphical representation when it’s assigned to something for displaying it, for example a SKLabelNode:
mySKLabelNode.Text = myUnicodeCharacterString // displays ”\u{25a1}” and not a hollow square
The problem boils down to this:
// A: direct approach, does works
let unicodeValueByValue = UnicodeScalar("\u{25a1}") // ”9633”
let c1 = Character(unicodeValueByValue) // ”a hollow square”
// B: indirect approach, this does not work
let myUnicodeString = "\u{25a1}"
let unicodeValueByVariable = UnicodeScalar(myUnicodeString) // Error: cannot find an initialiser
let c2 = Character(unicodeValueByVariable)
So, how do I display a unicode character of the format "\u{xxxx}" if it's not directly given in code?

Answer 1

A better way would be to use the proper \uNNNN escape sequence
for Unicode characters in JSON (see http://json.org for details).
This is automatically handled by NSJSONSerialization, and you don't
have to convert a hex code.
In your case the JSON data should be
{
"myUnicodeCharacter" : "\u25a1"
}
Here is a full self-contained example:
let jsonString = "{ \"myUnicodeCharacter\" : \"\\u25a1\"}"
println(jsonString)
// { "myUnicodeCharacter" : "\u25a1"}
let dict = NSJSONSerialization.JSONObjectWithData(jsonString.dataUsingEncoding(NSUTF8StringEncoding)!,
options: nil, error: nil) as [String : String]
let myUnicodeCharacterString = dict["myUnicodeCharacter"]!
println(myUnicodeCharacterString)
// □

Answer 2

I came up with a solution, which does not answer the question, but is actually a better way of doing what I'm trying to do.
The unicode character is given instead as its hexadecimal value in the JSON data file, stripping all escape characters:
{
”myUnicodeCharacter”: ”25a1”
}
Then it's processed like this, after reading the value in to myUnicodeCharacterString:
let num = Int(strtoul(myUnicodeCharacterString, nil, 16))
mySKLabelNode.Text = String(UnicodeScalar(num))
And that worked. Now the hollow square showed up.

Answer 3

In Swift, we can implement the following solution
let jsonString = "{ "unicodeCharacter" : "\u00BD"}"
let data = jsonString.data(using: .utf8)
if let data = data {
let dict = try? JSONSerialization.jsonObject(with: data, options: []) as? [String: String]
print(dict?["unicodeCharacter"] ?? "")
}
Output: "½\n"