Convert JSON feed to NSDictionary - ios

Question

Where JSON_CATEGORY_DATA_URL_STRING is my feed URL, which returns fine as:
[
{
"group":"For Sale",
"code":"SSSS"
},
{
"group":"For Sale",
"category":"Wanted",
"code":"SWNT"
}
]
I cannot seem to get a nice NSDictionary (or NSArray) out of the following code:
+ (NSDictionary *)downloadJSON
{
NSDictionary *json_string;
NSString *dataURL = [NSString stringWithFormat:#"%#", JSON_CATEGORY_DATA_URL_STRING];
NSLog(#"%#",dataURL);
NSURLRequest *request = [NSURLRequest requestWithURL:[NSURL URLWithString:dataURL]];
NSData *response = [NSURLConnection sendSynchronousRequest:request returningResponse:nil error:nil];
json_string = [[[NSString alloc] initWithData:response encoding:NSUTF8StringEncoding]autorelease];
NSDictionary *json_dict = (NSDictionary *)json_string;
NSLog(#"json_dict\n%#",json_dict);
NSLog(#"json_string\n%#",json_string);
return json_string;
}
I've read many posts on this, but am not getting it.

Answer 1

With IOS5 you can use NSJSONSerialization for serializing the JSON.
NSDictionary *dictionary = [NSJSONSerialization JSONObjectWithData:data options:kNilOptions error:&error];

Answer 2

You can't just cast a string as a dictionary and expect it to parse the JSON. You must use a JSON parsing library to take that string and convert it into a dictionary.

Answer 3

I made a class that makes this task easier. It uses iOS 5's NSJSONSerialization. Clone it from github here.

Answer 4

You need to use JSON parser. here is the edited code
+ (NSDictionary *)downloadJSON
{
NSDictionary *json_string;
NSString *dataURL = [NSString stringWithFormat:#"%#", JSON_CATEGORY_DATA_URL_STRING];
NSLog(#"%#",dataURL);
NSURLRequest *request = [NSURLRequest requestWithURL:[NSURL URLWithString:dataURL]];
NSData *response = [NSURLConnection sendSynchronousRequest:request returningResponse:nil error:nil];
json_string = [[[NSString alloc] initWithData:response encoding:NSUTF8StringEncoding]autorelease];
//JSONValue is a function that will return the appropriate object like dictionary or array depending on your json string.
NSDictionary *json_dict = [json_string JSONValue];
NSLog(#"json_dict\n%#",json_dict);
NSLog(#"json_string\n%#",json_string);
return json_dict;
}
this should be the code to get the NSDictionary. but you json string is an array so instead use .
+ (NSArray *)downloadJSON
{
NSDictionary *json_string;
NSString *dataURL = [NSString stringWithFormat:#"%#", JSON_CATEGORY_DATA_URL_STRING];
NSLog(#"%#",dataURL);
NSURLRequest *request = [NSURLRequest requestWithURL:[NSURL URLWithString:dataURL]];
NSData *response = [NSURLConnection sendSynchronousRequest:request returningResponse:nil error:nil];
json_string = [[[NSString alloc] initWithData:response encoding:NSUTF8StringEncoding]autorelease];
NSArray *json_dict = [json_string JSONValue];
NSLog(#"json_dict\n%#",json_dict);
NSLog(#"json_string\n%#",json_string);
return json_dict;
}
Edit:
you need to use JSON.framework to call JSONValue method.
also you need to return json_dict instead of json_string as json_string is of NSString type and not NSDictionary or NSArray.
and dont autorelease it, as it is your class variable

Answer 5

create method to fetchjson data.Pass your url in urlwithstring.
-(void)fetchjsondata
{
NSString *login= [[NSString stringWithFormat:#"your url string"]stringByAddingPercentEscapesUsingEncoding:NSUTF8StringEncoding];
NSLog(#"----%#", login);
NSURL *url = [NSURL URLWithString:[login stringByAddingPercentEscapesUsingEncoding:NSUTF8StringEncoding]];
//-- Get request and response though URL
NSMutableURLRequest *request = [[NSMutableURLRequest alloc]initWithURL:url];
[NSURLConnection sendAsynchronousRequest:request
queue:[NSOperationQueue mainQueue]
completionHandler:^(NSURLResponse *response, NSData *data, NSError *error) {
dispatch_async(dispatch_get_main_queue(), ^{
if (data) {
dic_property= [NSJSONSerialization JSONObjectWithData:data options:NSJSONReadingMutableContainers error:nil];
NSLog(#"%#", dic_property);
NSLog(#"counts=%d",[[dic_property objectForKey:#"Data"]count]);
}
else {
NSLog(#"network error, %#", [error localizedFailureReason]);
}
});
}];
}
call fetchjsonmethod in anywhere.
[NSThread detachNewThreadSelector:#selector(fetchdata) toTarget:self withObject:nil];