SwiftyJSON - Unable to get transactionId from JSON String - json

Question

I am using CocoaAsyncSocket to retrieve a message from a servers API that's using JSON. I am able to get the data and convert it to a printable string, what I am unable to do is retrieve a value (transactionId) from my attempts to parse the JSON string I already have, using SwiftyJSON. I know there are other posts that are similar to this one but none have solved my problem.
In ViewController:
func socket(_ sock: GCDAsyncSocket, didRead data: Data, withTag tag: Int) {
guard let msg = String(data: data, encoding: .utf8) else { return }
var response = " "
if msg.contains("Reset") {
transactionID = ParseJSON().parse(message: msg)
response = String(format: "{\"Response\":{\"transactionId\":\"%#%\",\"content\":{\"Reset\":{}}}}", transactionID)
socket.write((response.data(using: .utf8))!, withTimeout: -1, tag: 0)
}
socket?.readData(withTimeout: -1, tag: 0)
}
ParseJSON class:
func parse (message: String) -> String {
var parsedMessage = " "
let json = JSON(parseJSON: message)
let transactionId = json["Request"]["transactionId"].stringValue
parsedMessage = transactionId
print(parsedMessage)
return parsedMessage
}
The result that is displayed is an empty transactionId value. Nothing prints or anything.
If you spot any errors in my code or have a better approach then please let me know!
Edit:
Here is the string I am attempting to parse:
{"Request": {"content": {"Reset": {}}, "transactionId": "f7c4d630-552b-46d9-a37d-44450537b48d"}}
Here is my output:
{\"Response\":{\"transactionId\":\"\",\"content\":{\"Reset\":{}}}}

Answer 1

The problem is not the code. Consider:
func parse(message: String) -> String {
let json = JSON(parseJSON: message)
return json["Request"]["transactionId"].stringValue
}
let input = """
{"Request": {"content": {"Reset": {}}, "transactionId": "f7c4d630-552b-46d9-a37d-44450537b48d"}}
"""
let transactionID = parse(message: input)
print("transactionId:", transactionID)
let response = String(format: "{\"Response\":{\"transactionId\":\"%#\",\"content\":{\"Reset\":{}}}}", transactionID)
print("response:", response)
The result of the above, as you’d expect, is:
transactionId: f7c4d630-552b-46d9-a37d-44450537b48d
response: {"Response":{"transactionId":"f7c4d630-552b-46d9-a37d-44450537b48d","content":{"Reset":{}}}}
So I suspect that the input message is not quite what you expected. So I might suggest adding some error handling so you can diagnose precisely where it is going wrong:
func parse(message: String) -> String {
let json = JSON(parseJSON: message)
if let error = json.error {
fatalError("JSON parsing error: \(error)")
}
let request = json["Request"]
if let error = request.error {
fatalError("request error: \(error)")
}
let transactionId = request["transactionId"]
if let error = transactionId.error {
fatalError("transactionId error: \(error)")
}
return transactionId.stringValue
}
Now, in practice, you probably wouldn’t use fatalError, but rather would do some graceful error handling (e.g. change parse such that it throws, then throw the errors encountered, if any, and then catch the error where you call parse and handle any runtime issues gracefully). But during this diagnostic process, fatalError is useful because it will stop your debugger at the offending line, simplifying your diagnostic process.
Bottom line, the request must not be quite in the form you expect. Note, it’s going to be very sensitive to capitalization, malformed JSON, etc. So, by looking at the errors provided by SwiftyJSON, you should be able to narrow down the issue quite quickly.
Below, you tell us that the Data is:
<7b225265 71756573 74223a20 7b22636f 6e74656e 74223a20 7b225265 73657422
3a207b7d 7d2c2022 7472616e 73616374 696f6e49 64223a20 22643937 36303036
622d3130 38302d34 3864652d 39323232 2d623139 63363663 35303164 31227d7d
00>
The problem is that last byte, 0x00. If you remove that, it works.
FWIW, when I convert that hex string back to a Data and run it through JSONSerialization, it confirms the diagnosis:
Error Domain=NSCocoaErrorDomain
Code=3840 "Garbage at end."
UserInfo={NSDebugDescription=Garbage at end.}
You need to figure out why that 0x00 was included in the end of your payload and remove it.