Swift, NSJSONSerialization and NSError

Question

The problem is when there is incomplete data NSJSONSerialization.JSONObjectWithData is crashing the application giving unexpectedly found nil while unwrappin

Answer 1

Swift 3 NSJSONSerialization sample (read json from file):

file data.json (example from here: http://json.org/example.html)

{
"glossary":{
"title":"example glossary",
"GlossDiv":{
    "title":"S",
    "GlossList":{
        "GlossEntry":{
            "ID":"SGML",
            "SortAs":"SGML",
            "GlossTerm":"Standard Generalized Markup Language",
            "Acronym":"SGML",
            "Abbrev":"ISO 8879:1986",
            "GlossDef":{
                "para":"A meta-markup language, used to create markup languages such as DocBook.",
                "GlossSeeAlso":[
                                "GML",
                                "XML"
                                ]
            },
            "GlossSee":"markup"
        }
    }
}
}
}

file JSONSerialization.swift

extension JSONSerialization {

enum Errors: Error {
    case NotDictionary
    case NotJSONFormat
}

public class func dictionary(data: Data, options opt: JSONSerialization.ReadingOptions) throws -> NSDictionary {
    do {
        let JSON = try JSONSerialization.jsonObject(with: data , options:opt)
        if let JSONDictionary = JSON as? NSDictionary {
            return JSONDictionary
        }
        throw Errors.NotDictionary
    }
    catch {
        throw Errors.NotJSONFormat
    }
}
}

Usage

 func readJsonFromFile() {
    if let path = Bundle.main.path(forResource: "data", ofType: "json") {
        if let data = NSData(contentsOfFile: path) as? Data {

            do {
                let dict = try JSONSerialization.dictionary(data: data, options: .allowFragments)
                print(dict)
            } catch let error {
                print("\(error)")
            }

        }
    }
}

Result (log screenshot)