How to extract the actual NSString from json object as NSArray - iphone

Question

I'm working with a large set of json and really just need the NSString representation of what's inside the NSArray -including all the { }
My question is this - is their a better way than simply looping through each NSArray inside the main NSArray and outputting the description one by one?
ie- the below is a start to this process but it's very brittle meaning I need to know each item inside the hat {} and this isn't something I actually care about. I just need the json string to move forward.
The working code is below (thank you in advance!)
NSString* responseString = [[NSString alloc] initWithData:responseData encoding:NSUTF8StringEncoding];
[responseData release];
NSArray* json = [responseString JSONValue];
NSArray* item = [json valueForKeyPath:#"d.data"];
NSArray* hatjson = [item objectForKey:#"hat"];
NSMutableString * result = [[NSMutableString alloc] init];
for (NSObject * obj in hatjson)
{
[result appendString:[obj description]];
}
NSLog(#"the hat json is .. %#", result);

Answer 1

// …
NSArray* hatjson = [item objectForKey:#"hat"];
NSString *result = [hatjson JSONRepresentation];
NSLog(#"the hat json is .. %#", result);
I’m assuming you’re using SBJSON for JSON parsing. SBJSON defines a category on NSObject that includes the method
- (NSString *)JSONRepresentation;
This method returns a string with the JSON representation of a given object so long as the object is an instance of a class which SBJSON can convert to JSON (e.g. strings, numbers, arrays, dictionaries).

Answer 2

I'm assuming you're using the JSON library from here: https://github.com/stig/json-framework
You're complaining that the code you provided is brittle, but it sounds like, for what you want, the situation is brittle, so I think it's ok for the code that access it to be brittle, as long as you put NSAsserts in there so that you know ASAP when your assumptions have been broken.
I think the most brittle aspect of the code you've shown is that it assumes you're getting back NSArrays, when it appears from how you're accessing it that it's actually giving you NSDictionaries.
For instance, reading your code, I conclude that the responseString represents a JSON nested map looking something like this:
{ "d": { "data": { "hat": "baseball cap" } } }
The question then is "do you ever expect the value corresponding to the "hat" key to ever have more than one value?" I would genericize this code like so:
NSString* responseString = [[[NSString alloc] initWithData: responseData encoding: NSUTF8StringEncoding] autorelease];
[responseData release];
id json = [responseString JSONValue];
id hatJSONValue = [json valueForKeyPath:#"d.data.hat"];
NSString* result = nil;
if ([hatJSONValue isKindOfClass: [NSArray class]] && [hatJSONValue count] == 1)
{
result = [[hatJSONValue lastObject] description];
}
else
{
NSAssert(NO, #"Assumptions about returned JSON were wrong.");
}
NSLog(#"the hat json is .. %#", result);
Generally speaking, you always have to make tradeoffs between writing non-brittle code and getting things done. The key should be that if your code is going to make assumptions, you should assert that they're true, so if the situation ever changes, you'll know!