CODEWITHSUNDEEP
jsonswift
daredevil1234
daredevil1234

Reputation: 1425

Formatting JSON in swift: Invalid type in JSON write (OS_dispatch_data)

I am trying to send a post request to and api that contains a list of "items" that can be either an image or text.

However, I keep getting an error (listed in Title)

Here is the code turning my objects into JSON

    var json = [String: Any]()
    var jsonItems = [Any]()

    for i in 0...(items.count - 1){

        var it = [String: Any]()
        if let imageData = items[i].image?.jpgData(){
            it["image"] = imageData
        }

        if let text = items[i].text{
            it["text"] = text
        }

        if i == 0 {
            it["is_profile"] = true
            it["face_detected"] = faceDetected
        }

        jsonItems.append(it)
    }
    json["items"] = jsonItems

Is there any reason why this would not be formatted correctly?

EDIT:

The jpgData function

func jpgData() -> Data? {
    return UIImageJPEGRepresentation(self, 0.8)
}

Example code that causes crash:

extension Dictionary {
    var json: String {
        let invalidJson = "Not a valid JSON"
        do {
            let jsonData = try JSONSerialization.data(withJSONObject: self, options: .prettyPrinted)
            return String(bytes: jsonData, encoding: String.Encoding.utf8) ?? invalidJson
        } catch {
            return invalidJson
        }
    }
}

In addition to my sample code, passing the created dict as the param for Alamofire requests, URLSession requests, etc all cause a crash with the error from the title

EDIT: Solution Image data did need to be encoded. Feels so obvious in hindsight. Base64 encoding worked for printing out the structure like in my extension, but for network requests I ended up using Alamofire's MultipartFormData class (a custom wrapper around it) and appended as an application/octet-stream for the mimetype. Wish I could use a facepalm emoji here. I accepted one of the two answers that talked about encoding that actually had sample code.

Upvotes: 1

Views: 292

Answers (2)

DionizB
DionizB

Reputation: 1507

After converting to JPEG Data try encoding to base64

let strBase64 = imageData.base64EncodedString(options: .lineLength64Characters)

Check this answer for more info Convert between UIImage and Base64 string

Upvotes: 1

Daniel T.
Daniel T.

Reputation: 33967

A Data cannot be put into JSON. The Data object will have to be encoded. Probably using base64 encoding.

Upvotes: 0

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