CODEWITHSUNDEEP
swiftstringnsdata
RobMac
RobMac

Reputation: 860

How to detect encoding in Data based on a String?

I'm loading a text file, the encoding is unknown as it comes from other sources. The content itself comes from macOS NSDocument's read method, which is fed into my model's read. The String constructor requires the encoding when using Data, if you assume the incorrect one you may get a null. I've created a conditional cascade of potential encodings (it's what other people seem to be doing), there's gotta be a better way to do this. Suggestions?

    override func read(from data: Data, ofType typeName: String) throws {
        model.read(from: data, ofType: typeName)
    }

In the model:

    func read(from data: Data, ofType typeName: String) {
        if let text = String(data: data, encoding: .utf8) {
            content = text
        } else if let text = String(data: data, encoding: .macOSRoman) {
            content = text
        } else if let text = String(data: data, encoding: .ascii) {
            content = text
        } else {
            content = "?????"
        }
    }

Upvotes: 2

Views: 4128

Answers (2)

Avicii4ever
Avicii4ever

Reputation: 135

Here is my approach based on @Leo Dabus's, work well on Xcode14.3

var stringEncoding: String.Encoding {
        var nsString: NSString?
        let rawValue = NSString.stringEncoding(for: self, encodingOptions: nil, convertedString: &nsString, usedLossyConversion: nil)
        return .init(rawValue: rawValue)
    }

Upvotes: 0

Leo Dabus
Leo Dabus

Reputation: 236458

You can extend Data and create a stringEncoding property to try to detect the string encoding. Try like this:

extension Data {
    var stringEncoding: String.Encoding? {
        var nsString: NSString?
        guard case let rawValue = NSString.stringEncoding(for: self, encodingOptions: nil, convertedString: &nsString, usedLossyConversion: nil), rawValue != 0 else { return nil }
        return .init(rawValue: rawValue)
    }
}

Then you can simply pass data.stringEncoding to the String initialer:

if let string = String(data: data, encoding: data.stringEncoding) {
    print(string)
}

Upvotes: 11

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