gistfile1.m

#import <Foundation/Foundation.h>

@interface DataModel : NSObject
@property (nonatomic, copy) NSString *email;
@property (nonatomic, copy) NSString *password;
@property (nonatomic, copy) NSString *sessionId;
@property (nonatomic, copy) NSString *deviceId;
@property (nonatomic, copy) NSString *encryptionKey;
@end

@implementation DataModel
@end

int main(int argc, char *argv[]) {
  	@autoreleasepool {
		
		NSMutableArray *dataModels = [NSMutableArray array];
		
		NSURLRequest *request = [NSURLRequest requestWithURL:[NSURL URLWithString:@"http://path/to/webAPI"]];
		
		NSURLResponse *response = nil;
		NSData *data = [NSURLConnection sendSynchronousRequest:request returningResponse:&response error:nil];
		
		if (data) {
			NSArray *JSON = [NSJSONSerialization JSONObjectWithData:data options:NSJSONReadingMutableContainers error:nil];
			if (JSON) {
			   	for (NSDictionary *item in JSON) {
				
				  	DataModel *dataModel = [[DataModel alloc] init];
					
					dataModel.email = [item valueForKeyPath:@"data.usr_email"];
					dataModel.password = [item valueForKeyPath:@"data.usr_pass"];
					dataModel.sessionId = [item valueForKeyPath:@"header.sess_id"];
					dataModel.deviceId = [item valueForKeyPath:@"header.device_id"];
					dataModel.encryptionKey = [item valueForKey:@"enc_key"];
					
					[dataModels addObject:dataModel];
			   	}
			}
		}
		
		NSLog(@"%@", dataModels);
	}
}