iOS parse string with multiple JSON objects? - ios

Question

I'm having some troubles when my app receives multiple JSON objects at the same time. I'm using a TCP socket that is open to my server which sends me messages. The reason i seem to recieve multiple messages is probably due to network lag.
This is what a server message can look like (i then put this into a NSString and try to parse the JSON):
{
"id": "156806",
"type": "message",
"userCity": "",
"userCountry": "",
"os": "",
"browser": "",
"trafficType": "",
"seKeyword": "",
"seType": "",
"currentPage": "",
"userId": "1",
"agentId": "352",
"customField1": "",
"visitorNick": "Visitor 147220060",
"msg": "asd",
"time": "16:05",
"channel": "V147220060",
"visits": "254"
} {
"type": "previewStopped",
"msg": "",
"visitorNick": "Mackan",
"customField1": "",
"visitorNick": "Visitor V147220060",
"time": "16:05",
"channel": "V147220060"
} {
"id": "156807",
"type": "message",
"userCity": "",
"userCountry": "",
"os": "",
"browser": "",
"trafficType": "",
"seKeyword": "",
"seType": "",
"currentPage": "",
"userId": "1",
"agentId": "352",
"customField1": "",
"visitorNick": "Visitor 147220060",
"msg": "as",
"time": "16:05",
"channel": "V147220060",
"visits": "254"
} {
"id": "156808",
"type": "message",
"userCity": "",
"userCountry": "",
"os": "",
"browser": "",
"trafficType": "",
"seKeyword": "",
"seType": "",
"currentPage": "",
"userId": "1",
"agentId": "352",
"customField1": "",
"visitorNick": "Visitor 147220060",
"msg": "da",
"time": "16:05",
"channel": "V147220060",
"visits": "254"
}
And here is how i currently parse the NSString, note that the above JSON is outputData in the code below:
// Parse the message from the server
NSError* error;
NSDictionary *JSON =
[NSJSONSerialization JSONObjectWithData: [outputData dataUsingEncoding:NSUTF8StringEncoding]
options: NSJSONReadingMutableContainers
error: &error];
NSString* type = [JSON objectForKey:#"type"];
if(error) {
NSLog(#"PARSE ERROR ------------->>>>> : %#\n", error);
}
NSLog(#"SERVER TYPE --> %#\n", type);
if([type isEqualToString:#"message"]) {
[self messageReceived:outputData];
}
The above works perfectly when i only recieve one JSON in outputData but when multiple JSONs are recieved it trows an error:
PARSE ERROR ------------->>>>> : Error Domain=NSCocoaErrorDomain
Code=3840 "The operation couldn’t be completed. (Cocoa error 3840.)"
(Garbage at end.) UserInfo=0x14e9acb0 {NSDebugDescription=Garbage at
end.}
Any ideas how to handle this?

Answer 1

Hmm...you could wrap it yourself. Take the data you get and prepend "{ "dataarray": [" to the beginning, and "] }" to the end. This will produce an array, the elements of which will be your individual JSON entities.

Answer 2

Try this:
NSData *jsonData = [outputData dataUsingEncoding:NSUTF8StringEncoding];
NSArray *dict = [NSJSONSerialization JSONObjectWithData:jsonData options:0 error:&e];
NSDictionary *JSON = [dict objectAtIndex:0];
NSString* type = [JSON objectForKey:#"type"];
EDIT:
An example of JSON, because your "" can cause problems:
{
aula = "AULA M04";
cuatrimestre = "Primer quadrimestre";
dia = Dimecres;
edificio = "AULARI V";
fin = "18:00";
inicio = "15:00";
}
Hope it helps!

Answer 3

It's erroring out because you don't have valid JSON in your string. You'll need to do something like the following to get it into the correct format:
NSString *formattedString = [NSString stringWithFormat:#"[%#]", [outputData stringByReplacingOccurrencesOfString:#"} {" withString:#"},{"]];
NSError *error = nil;
NSArray *JSON = [NSJSONSerialization JSONObjectWithData:[formattedString dataUsingEncoding:NSUTF8StringEncoding] options:NSJSONReadingAllowFragments error:&error];
That is assuming outputData is an NSString.

Answer 4

If your data stream contains multiple JSONs in sequence, it strictly isn't JSON anymore. Rather, it is a custom protocol which embeds JSON.
You need to first define your custom protocol. It can be defined as an arbitrary number of JSONs in sequence - if this fits your needs. NSJSONSerialization isn't capable to parse your custom protocol, though.
You could define your protocol differently, for example: your data is a contiguous stream of messages, where a message is a "blob" prepended by value representing the length in bytes, e.g.:
message := message_size CRLF blob
message_size := digits
data := message*
That is, your data may look as follows:
2\n\r[]4\n\r5["a"]
This is of course a pretty naive protocol, but it should be sufficient to demonstrate the basic idea.
Your blob could then be JSON UTF-8.
This "protocol" can be easily parsed with a custom parser, where the "blob" (a single JSON) will be passed through a JSON parser, possibly wrapped into a NSData object.