Convert nested JSON to Data object in Swift 4

Question

I have to send a URLRequest containing a JSON object as its http-body (which needs to be of type Data).

My JSON looks like this:

let json: [String : Any] = [
        "to" : toDeviceToken,       // String
            "notification" : [
                "title" : title,    // String
                "body" : body,      // String
                "icon" : icon       // UIImage
            ],
            "data" : {
                // Add optional data here.
            }
        ]

And I would like to convert this to type Data in order to put it into a URLRequest.

This

try JSONSerialization.data(withJSONObject: json, options: .prettyPrinted)

always fails for some reason, maybe because it is a nested JSON object? In addition, JSONSerialization.isValidJSONObject(json) returns false.

When turning the UIImage object into a String object like this UIImagePNGRepresentation(UIImage.appIcon!)?.base64EncodedString(), I get an error saying 'Invalid type in JSON write (_SwiftValue)'

How would I do that?

@LouFranco This does not work for me, maybe because it's a nested JSOn object? — j3141592653589793238
– j3141592653589793238, Commented Jan 20, 2018 at 22:51
FYI, people often use multipart/form-data requests when uploading an image, as the base64 string representation introduces 33% overhead. If it's a small image, that's inconsequential. But if it's a large image or if you're uploading many, it can start to become material. Tools like Alamofire make uploading multipart/form-data requests really easy. But if doing it manually, the code is a little more tedious. — Rob
– Rob, Commented Jan 20, 2018 at 23:53
I would also suggest using JPEG representation which will reduce considerably the data size — Leo Dabus
– Leo Dabus, Commented Jan 21, 2018 at 0:10

rmaddy · Accepted Answer · 2018-01-20 22:58:26Z

1

Your code fails because it contains data that can't be converted to JSON.

See the documentation for JSONSerialization for a list of support data types. Note that UIImage is not one of the supported types.

You will need to convert the UIImage to a string using a base64 encoding of its JPG or PNG representation.

answered Jan 20, 2018 at 22:58

rmaddy

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j3141592653589793238 Over a year ago

UIImagePNGRepresentation(UIImage.appIcon!)?.base64EncodedString() So this code should work, but it always throws a very long error 'Invalid type in JSON write (_SwiftValue)'

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