How to parse json specific fields using objective-c - objective-c

Question

I'm trying to parse a very simple json object with 1 value. (ocUnit test below)
- (void) testHatCartParseWithValidRefId {
NSString* data = #"{\"refid\":999}";
Cart* obj = [HatCartParseJson parseJsonAndReturnObject:data];
STAssertTrue([obj.refid isEqualToString:#"999"], #"fail");
}
In the implementation everything fails when I add the line to pull it from either key or index. How should I pull this from the json input? Please keep in mind I need this json parse (not string) the actual code I'm working with is a large set of JSON data.
+ (Cart *) parseJsonAndReturnObject:(NSString *)json
{
NSArray* cart = [json JSONValue];
for (NSDictionary* item in cart) {
Cart* obj = [[Cart alloc] init];
//NSString* refid = [item objectAtIndex:0];
//NSString* refid = [item objectForKey:#"refid"];
[obj setRefid:#"999"];
return obj;
}
return nil;
}
Thank you in advance

Answer 1

You are expecting that the return value of JSONValue is an NSArray, which in this case it isn't.
So, you must do a check if the return value is actually an NSArray, and if it is, then iterate through the collection, otherwise check if it's an NSDictionary, and if it is, then return the Cart object with the refid from the NSDictionary. If all of this fails, then just return nil.
As a side point, according to Apple's Object Ownership Policy, you should return autorelease-d objects from methods whose names do not contain the words "alloc", "new" or "copy". This would be one such method where you'd return an autorelease-d object.
+ (Cart *) parseJsonAndReturnObject:(NSString *)json
{
id cart = [json JSONValue];
NSString* refid = nil;
if([cart isKindOfClass:[NSArray class]]) {
refid = [[cart objectAtIndex:0] objectForKey:#"refid"];
} else if([cart isKindOfClass:[NSDictionary class]]) {
refid = [cart objectForKey:#"refid"];
}
if(refid) {
Cart* c = [[Cart alloc] init];
[c setRefid:refid];
return [c autorelease];
}
return nil;
}