Question

My application returns a NSMutableData *receivedData.

I’ve opted for using NSJSONSerialization to parse this under the assumption that it would be easiest. I’m having extreme trouble trying to get my head around how to do it. I’m very new to Objective-C, from a Java background.

In Java I used gson to parse the JSON in to an array which I could use easily. I’m really struggling with this here.

My current code for parsing the JSON is:

NSError *e = nil;
    NSArray *jsonArray = [NSJSONSerialization JSONObjectWithData: receivedData options: NSJSONReadingMutableContainers error: &e];

    if (!jsonArray) {
        NSLog(@"Error parsing JSON: %@", e);
    } else {
        for(NSDictionary *item in jsonArray) {
            NSLog(@"Item: %@", item);
        }
    }

As provided by somebody on the internet. This works and prints two items to NSLog. result and header. Here is how the JSON looks:

{
  "header":{
    "session":"sessionid",
    "serviceVersion":"1",
    "prefetchEnabled":true
  },
  "result":"50ce82401e826"
}

However if there is an error the JSON can also look like this:

{
  "header":{
    "session":"sessionid",
    "serviceVersion":"1",
    "prefetchEnabled":true
  },
  "fault":{
    "code":0,
    "message":"someErrorCode"
  }
}

How I want the code to work:

1. Check if there is a “fault” object
2. If there is, print fault.code and fault.message to NSLog
3. If there isn’t, I know that my JSON contains result instead of fault
4. Print the value of result to NSLog

But I can’t for the life of me figure out how to approach it. Can someone please give me some pointers?

Answer 1

your object appears to be a dictionary.

Try this out.

NSError *e = nil;
id jsonObj = [NSJSONSerialization JSONObjectWithData: receivedData options: NSJSONReadingMutableContainers error: &e];

NSArray *jsonArray = nil;
NSDictionary *jsonDict = nil;

if ([jsonObj isKindOfClass:[NSArray class]]){
    jsonArray = (NSArray*)jsonObj;
}
else if ([jsonObj isKindOfClass:[NSDictionary class]]){
    jsonDict = (NSDictionary*)jsonObj;
}

if (jsonArray != nil) {
    // you have an array;
    for(NSDictionary *item in jsonArray) {
        NSLog(@"Item: %@", item);
    }
}
else if (jsonDict != nil){
    for (NSString *key in jsonDict.allKeys){
        NSLog(@"Key: %@ forItem: %@",key,[jsonDict valueForKey:key]);
    }
}
else {
    NSLog(@"Error: %@",e);
}