Swift using String to create JSON object

Question

I am trying to use a string I am getting from a database as JSON using swift. I have tried to convert the string to a data object and then use JSONSerialization, but the results always come back nil.

Here is a sample of my code:

var string = "{Param1: \"Value\", Param2: \"value2\", Param3: \"value3\"}"
let data = (reducedOptionsString as NSString).dataUsingEncoding(NSUTF8StringEncoding)
if let d = data{
    var err : NSErrorPointer = nil
    let parsedObject: AnyObject? = NSJSONSerialization.JSONObjectWithData(d, options: NSJSONReadingOptions.MutableLeaves, error: err)
    if let dict = parsedObject as? Dictionary<String, AnyObject>{
          ...
    }
}

For some reason parsedObject always comes back as nil

Does anyone know what I might be missing to convert my string data to a JSON object that I can use?

Why are you ignoring the error parameter? Print it out on failure. — zaph
– zaph, Commented Jun 18, 2015 at 3:58
The code is incorrect, string is not used and reducedOptionsString is undefined. I guess they are the same. — zaph
– zaph, Commented Jun 18, 2015 at 4:09

Claudio Redi · Accepted Answer · 2015-06-18 14:43:49Z

Your json is not valid, keys must me enclosed in quotes too.

"{ \"Param1\": \"Value\", \"Param2\": \"value2\", \"Param3\": \"value3\"}"

Also, as @zaph pointed out, it's variable string the one you want to convert to data.

var string = "{\"Param1\": \"Value\", \"Param2\": \"value2\", \"Param3\": \"value3\"}"
if let data = string.dataUsingEncoding(NSUTF8StringEncoding){
    var err : NSErrorPointer = nil
    let parsedObject = NSJSONSerialization.JSONObjectWithData(
        data!,
        options: NSJSONReadingOptions.MutableLeaves, 
        error: err) as? Dictionary<String, AnyObject>

    if (parsedObject != nil) {
        ...
    }
    else {
        if (err != nil) {
            println("Error: \(err)")
        }
        else {
            println("Error: unexpected error parsing json string")
        }
    }
}

Alternatively, you could use SwiftyJSON, a very popular library to handle json on swift that could make your life a little easier.

James Takarashy · Accepted Answer · 2015-06-18 04:54:25Z

3

    var string = "{\"Param1\": \"Value\", \"Param2\": \"value2\", \"Param3\": \"value3\"}"

    if let data = (string as NSString).dataUsingEncoding(NSUTF8StringEncoding)
    {
        var err : NSErrorPointer = nil
        let parsedObject: AnyObject? = NSJSONSerialization.JSONObjectWithData(data, options:    NSJSONReadingOptions.MutableLeaves, error: err)

        if (err != nil)
        {
            println("error handling...")
        }

        if let dict = parsedObject as? Dictionary<String, AnyObject>
        {
            println("XD")
        }
    }

answered Jun 18, 2015 at 4:54

James Takarashy

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1 Comment

James Takarashy Over a year ago

Hehehehe :), just a smiley since I can't stand empty if statements in code and writing "..." will force you to replace this line when copying to your project, even if you just wanted to test if it compiles... So, it makes life easier, just by a little bit ;)

JJRS · Accepted Answer · 2015-06-18 10:46:16Z

1

You just replace following 2 lines in your OWN code, rest will be work fine. :)

var string = "{\"Param1\": \"Value\", \"Param2\": \"value2\", \"Param3\": \"value3\"}"
let data = (string as NSString).dataUsingEncoding(NSUTF8StringEncoding)

answered Jun 18, 2015 at 10:46

JJRS

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Comments

Mike Zriel · Accepted Answer · 2021-07-20 14:50:19Z

1

Swift 5 Example:

let properties: [(String, Any?)] = [("firstName", firstName),
                                        ("lastName", lastName),
                                        ("city", city),
                                        ("state", state),
                                        ("zipCode", zipCode),
                                        ("country", country)]

let body = properties.compactMap({ property -> (String, Any)? in
        if let value = property.1 {
            return (property.0, value)
        } else {
            return nil
        }
    })

let jsonDict = Dictionary(uniqueKeysWithValues: body)
let jsonData = try? JSONSerialization.data(withJSONObject: jsonDict, options: [])

answered Jul 20, 2021 at 14:50

Mike Zriel

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