JSON to Objective-C Dictionary - objective-c

Question

I'm making URL Request to an API but I dont know how to render the JSON, It generates an array of multiple users like this [{"user": "value"}, {"user":"value"}] and I was trying to use a TableView so I need an NSDictionary but i think is better to render a JSON like {users: [{"user": "value"}, {"user":"value"}]}. I have this code to make the request
#import "JSONKit.h"
NSError *error = nil;
NSURLResponse *response = nil;
NSMutableURLRequest *request = [[NSMutableURLRequest alloc] initWithURL: [NSURL URLWithString: #"http://localhost:3000/getusers"]];
[request setHTTPMethod:#"GET"];
NSData *jsonData = [NSURLConnection sendSynchronousRequest:request returningResponse:&response error:&error];
users = [[jsonData objectFromJSONData] objectForKey:#"users"];
usersKeys = [users allKeys];
but I'm getting this error
2012-09-16 18:51:11.360 tableview[2979:c07] -[JKArray allKeys]: unrecognized selector sent to instance 0x6d30180
2012-09-16 18:51:11.362 tableview[2979:c07] * Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '-[JKArray allKeys]: unrecognized selector sent to instance 0x6d30180'
I dont really know how to accomplish this so any help is useful, thanks

Answer 1

You are getting that error because whatever got parsed out of "jsonData" isn't necessarily what you expected (i.e. a dictionary).
Perhaps you need some error checking in that code of yours.
For example:
NSData *jsonData = [NSURLConnection sendSynchronousRequest:request returningResponse:&response error:&error];
if(jsonData)
{
id objectReturnedFromJSON = [jsonData objectFromJSONData];
if(objectReturnedFromJSON)
{
if([objectReturnedFromJSON isKindOfClass:[NSDictonary class]])
{
NSDictionary * dictionaryFromJSON = (NSDictionary *)objectReturnedFromJSON;
// assuming you declared "users" & "usersKeys" in your interface,
// or somewhere else in this method
users = [dictionaryFromJSON objectForKey:#"users"];
if(users)
{
usersKeys = [users allKeys];
} else {
NSLog( #"no users in the json data");
}
} else {
NSLog( #"no dictionary from the data returned by the server... check the data to see if it's valid JSON");
}
} else {
NSLog( #"nothing valid returned from the server...");
}
} else {
NSLog( #"no data back from the server");
}

Answer 2

I was thinking on something like this
NSError *error = nil;
NSURLResponse *response = nil;
NSMutableURLRequest *request = [[NSMutableURLRequest alloc] initWithURL: [NSURL URLWithString: #"http://localhost:3000/getusers"]];
[request setHTTPMethod:#"GET"];
NSData *jsonData = [NSURLConnection sendSynchronousRequest:request returningResponse:&response error:&error];
JSONDecoder *decoder = [[JSONDecoder alloc]
initWithParseOptions:JKParseOptionNone];
NSArray *json = [decoder objectWithData:jsonData];
NSMutableArray *objects = [[NSMutableArray alloc] init];
NSMutableArray *keys = [[NSMutableArray alloc] init];
for (NSDictionary *user in json) {
[objects addObject:[user objectForKey:#"user" ]];
[keys addObject:[user objectForKey:#"value" ]];
}
users = [[NSDictionary alloc] initWithObjects:objects forKeys:keys];
NSLog(#"users: %#", users);
usersKeys = [users allKeys];
But it doesnt look efficient for many items or im wrong?