Singleton for making get-post requests (passing in external block, completion handler)

singleton.m

//
//  singleton.m
//

#import "singleton.h"

typedef void(^ CompletionBlock)(NSData*, NSURLResponse*, NSError*);

@implementation singleton
@synthesize vData;

- (id)init {
    
    if (self = [super init]) {
    
        // The master object
        vData = [[NSMutableDictionary alloc]init];
        
    }
    return self;
}

+ (id) sharedSingleton {
    static singleton *sharedSingleton = nil;
    static dispatch_once_t onceToken;
    dispatch_once(&onceToken, ^{
        sharedSingleton = [[self alloc] init];
    });
    return sharedSingleton;
}

- (void) performGetRequestWithURL: (NSURL *) url withCompletionHandler: (CompletionBlock) theBlock {


    // GET SIMPLE: how to use this function from outside the singleton
    /*
    NSURL *url = [routes auth_authenticate];
    
    void (^theBlock) (NSData*, NSURLResponse*, NSError*) = ^(NSData *data, NSURLResponse *response, NSError *error) {
        NSLog(@"Got response %@ with error %@.\n", response, error);
        NSLog(@"DATA:\n%@\nEND DATA\n", [[NSString alloc] initWithData:data encoding:NSUTF8StringEncoding]);
    };
    
    [s performGetRequestWithURL:url withCompletionHandler:theBlock];
    */
    

    NSLog(@"performGetRequest");

    NSURLSessionConfiguration *defaultConfiguration = [NSURLSessionConfiguration defaultSessionConfiguration];
    NSURLSession *sessionWithoutADelegate = [NSURLSession sessionWithConfiguration:defaultConfiguration];    
    [[sessionWithoutADelegate dataTaskWithURL:url completionHandler:theBlock] resume];

}

- (void) performPostRequestWithURL:(NSURL *)url withDictionary:(NSMutableDictionary *)dictionary withCompletionHandler: (CompletionBlock) theBlock {

    // POST SIMPLE: how to use this function from outside the singleton.
    
    /*
    
    NSURL *url = [routes auth_authenticate];
    
    NSMutableDictionary *dictionaryParameters = [[NSMutableDictionary alloc]init];
    
    NSString *email = [s.vData objectForKey:@"email"];
    NSString *password = [s.vData objectForKey:@"password"];
    [dictionaryParameters setValue:email forKey:@"email"];
    [dictionaryParameters setValue:password forKey:@"password"];
    
    void (^theBlock) (NSData*, NSURLResponse*, NSError*) = ^(NSData *data, NSURLResponse *response, NSError *error) {    
    
        singleton *s = [singleton sharedSingleton];
        
        NSDictionary *JSON = [NSJSONSerialization JSONObjectWithData:data options:NSJSONReadingMutableContainers error:&error];
        NSLog([JSON description]);
    
    };
    
    [s performPostRequestWithURL:url withDictionary:dictionaryParameters withCompletionHandler:theBlock];
    
    */

    NSError *error;

    NSURLSessionConfiguration *configuration = [NSURLSessionConfiguration defaultSessionConfiguration];
    NSURLSession *session = [NSURLSession sessionWithConfiguration:configuration delegate:self delegateQueue:nil];
    NSMutableURLRequest *request = [NSMutableURLRequest requestWithURL:url cachePolicy:NSURLRequestUseProtocolCachePolicy timeoutInterval:60.0];

    [request setValue:@"application/json" forHTTPHeaderField:@"Content-type"];
    [request setValue:@"application/json" forHTTPHeaderField:@"Accept"];
    [request setHTTPMethod:@"POST"];
        
    NSData *postData = [NSJSONSerialization dataWithJSONObject:dictionary options:0 error:&error];
    [request setHTTPBody:postData];

    NSURLSessionDataTask *postDataTask = [session dataTaskWithRequest:request completionHandler:theBlock];
    [postDataTask resume];    
    
}

@end