Parsing JSON data in iOS [duplicate] - objective-c

Question

This question already has answers here:
Closed 10 years ago.
Possible Duplicate:
iPhone/iOS JSON parsing tutorial
I have been reading many tutorials on how to parse JSON data in Objective C but still I am unable to figure it out. I want to parse data from the JSON file and show it up on screen.
For example,
I want to parse data from here and get all the values of different retailers in different variables, so that I can use them later.
How can I do it?

Answer 1

Assuming that you have your data in a NSData object you can use NSJSONSerialization class available in iOS 5 and up.
+ (id)JSONObjectWithData:(NSData *)data options:(NSJSONReadingOptions)opt error:(NSError **)error
This is a class method that will convert your data into objects like NSArray, NSDictionary, NSNumber etc. depending on the contents of your data object.

Answer 2

Here is how you would download and parse the data from a web server. Note that all these methods are part of the same class and there are instance variables named _downloadData of type NSMutableData* and _downloadConnection of type NSURLConnection*. Also note this code assumes ARC is not being used. If it is, just remove the object releases and retains and make sure the instance variables are strong references.
-(void)startDownload {
NSURL* jsonURL = [NSURL URLWithString:#"http://isbn.net.in/9781449394707.json"];
NSMutableURLRequest* request = [NSMutableURLRequest requestWithURL:jsonURL cachePolicy:NSURLRequestReloadIgnoringLocalCacheData timeoutInterval:60];
_downloadData = [[NSMutableData dataWithCapacity:512] retain];
_downloadConnection = [[NSURLConnection alloc] initWithRequest:request delegate:self startImmediately:YES];
}
- (void)connection:(NSURLConnection *)connection didReceiveResponse:(NSURLResponse *)response
{
[_downloadData setLength:0];
}
- (void)connection:(NSURLConnection *)connection didReceiveData:(NSData *)data
{
[_downloadData appendData:data];
}
- (void) connection:(NSURLConnection *)connection didFailWithError:(NSError *)error
{
[_downloadConnection release];
_downloadConnection = nil;
[_downloadData release];
_downloadData = nil;
}
- (void) connectionDidFinishLoading:(NSURLConnection *)connection
{
NSError* jsonError = nil;
NSDictionary* jsonDict = nil; // your data will come out as a NSDictionry from the parser
jsonDict = [NSJSONSerialization JSONObjectWithData:_downloadData options:NSJSONReadingMutableLeaves error:&jsonError];
if ( nil != jsonError ) {
// do something about the error
return;
}
[_downloadConnection release];
_downloadConnection = nil;
[_downloadData release];
_downloadData = nil;
// now do whatever you want with your data in the 'jsonDict'
}