How do I access an AFHTTPRequest's Completion Block? - objective-c

Question

I'm posting a notification in the request failure block:
[manager POST:path
parameters:nil
success:^(AFHTTPRequestOperation *operation, id responseObject) {
if (operation.response.statusCode == 200) {
//message delegate
}
} failure:^(AFHTTPRequestOperation *operation, NSError *error) {
[[NSNotificationCenter defaultCenter] postNotificationName:HOST_UNREACHABLE object:operation];
}];
In the method that receives the notification, the completionBlock attribute is nil.
How do I access it without subclassing & overriding?

Answer 1

First to answer the question of how to send a block to an NSNotification:
The way you're attempting to do it is dangerous, because we don't know how AFHTTPSessionManager handles the blocks you pass it, and, unless its in the public interface, what it does may not remain fixed over time.
So, make a local variable to represent the block you want to pass, say, the completionBlock...
// this is a local variable declaration of the block
void (^completionBlock)(AFHTTPRequestOperation*,id) = ^(AFHTTPRequestOperation *operation, id response) {
if (operation.response.statusCode == 200) {
//message delegate
}
};
[manager POST:path
parameters:nil
success:completionBlock
} failure:^(AFHTTPRequestOperation *operation, NSError *error) {
[[NSNotificationCenter defaultCenter] postNotificationName:HOST_UNREACHABLE object:completionBlock];
}];
The observer can get the block and invoke it this way...
- (void)didReceiveNotification:(NSNotification *)notification {
void (^completionBlock)(AFHTTPRequestOperation*,id) = notification.object;
// use it
[manager POST:someOtherPath
parameters:nil
success:completionBlock
// etc.
];
}
But I think the approach is strange. It spreads out responsibility for making the request to the object that gets notified, leaving it needing to know the path to retry the parameters (which you don't have in this case, but you might one day).
Consider instead subclassing the manager and adding behavior that does the retry. Now your manager subclass can be in charge of all requests, including retries, and your other classes are just customers who handle the outcome. Something like...
#interface MyAFHTTPRequestManager : AFHTTPSessionManager
- (nullable NSURLSessionDataTask *)POST:(NSString *)URLString
retryURL:(NSString *)retryURLString
parameters:(nullable id)parameters
success:(nullable void (^)(NSURLSessionDataTask *task, id responseObject))success
failure:(nullable void (^)(NSURLSessionDataTask *task, NSError *error))failure;
#end
Have your subclass implementation call super with the first URLString, and upon failure, call super with the retryURLString. e.g.
- (nullable NSURLSessionDataTask *)POST:(NSString *)URLString
retryURL:(NSString *)retryURLString
parameters:(nullable id)parameters
success:(nullable void (^)(NSURLSessionDataTask *task, id responseObject))success
failure:(nullable void (^)(NSURLSessionDataTask *task, NSError *error))failure {
[super POST:URLString parameters:parameters success:success
failure:^(AFHTTPRequestOperation *operation, NSError *error) {
[super POST:retryURLString parameters:parameters success:success failure:failure];
}];
}