CODEWITHSUNDEEP
objective-cobjective-c-blocks
Boon
Boon

Reputation: 41500

In AFNetworking, why are some return objects declared as __block type?

AFNetworking code has a few places in which __block is used for objects in methods where there is no obvious need to change the object. For example, In AFHTTPSessionManager, the GET call uses __block on the task object. Any idea why?

- (NSURLSessionDataTask *)GET:(NSString *)URLString
                   parameters:(NSDictionary *)parameters
                      success:(void (^)(NSURLSessionDataTask *task, id responseObject))success
                      failure:(void (^)(NSURLSessionDataTask *task, NSError *error))failure
{
    NSMutableURLRequest *request = [self.requestSerializer requestWithMethod:@"GET" URLString:[[NSURL URLWithString:URLString relativeToURL:self.baseURL] absoluteString] parameters:parameters];

    __block NSURLSessionDataTask *task = [self dataTaskWithRequest:request completionHandler:^(NSURLResponse * __unused response, id responseObject, NSError *error) {
        if (error) {
            if (failure) {
                failure(task, error);
            }
        } else {
            if (success) {
                success(task, responseObject);
            }
        }
    }];

    [task resume];

    return task;
}

Similarly in other classes, __block is used for objects, as shown below for credential object.

- (void)URLSession:(NSURLSession *)session
didReceiveChallenge:(NSURLAuthenticationChallenge *)challenge
 completionHandler:(void (^)(NSURLSessionAuthChallengeDisposition disposition, NSURLCredential *credential))completionHandler
{
    NSURLSessionAuthChallengeDisposition disposition = NSURLSessionAuthChallengePerformDefaultHandling;
    __block NSURLCredential *credential = nil;

    if (self.sessionDidReceiveAuthenticationChallenge) {
        disposition = self.sessionDidReceiveAuthenticationChallenge(session, challenge, &credential);
    } else {
        if ([challenge.protectionSpace.authenticationMethod isEqualToString:NSURLAuthenticationMethodServerTrust]) {
            if ([self.securityPolicy evaluateServerTrust:challenge.protectionSpace.serverTrust]) {
                credential = [NSURLCredential credentialForTrust:challenge.protectionSpace.serverTrust];
                if (credential) {
                    disposition = NSURLSessionAuthChallengeUseCredential;
                } else {
                    disposition = NSURLSessionAuthChallengePerformDefaultHandling;
                }
            } else {
                disposition = NSURLSessionAuthChallengeCancelAuthenticationChallenge;
            }
        } else {
            disposition = NSURLSessionAuthChallengePerformDefaultHandling;
        }
    }

    if (completionHandler) {
        completionHandler(disposition, credential);
    }
}

Upvotes: 1

Views: 260

Answers (1)

newacct
newacct

Reputation: 122449

In both of these places, __block is useless and unnecessary.

In the first case, the variable task is not assigned to after initialization on the line where it is defined. __block is only useful if the variable is assigned to (and for non-retaining purposes in MRC), so it is pointless here.

In the second case, the variable credential is not captured in a block at all, so again it is useless.

Upvotes: 1

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