A cleaner version of the previous code without some of the __weak, __strong line noise. Recursive completion blocks in ObjC using some higher order functions.

gistfile1.m

#import <Foundation/Foundation.h>

typedef void(^CompletionHandler)(id connection, id result, NSError * error);
typedef BOOL(^Counter)();
typedef void(^RequestWrapperComp)();

@interface SMRequestFoo : NSObject
+(void)
    request   :(id               ) thing
    completion:(CompletionHandler) completion;
@end
@implementation SMRequestFoo
+(void)
    request   :(id               ) thing
    completion:(CompletionHandler) completion
{
    static int count_through = 0;
    
    NSError * error        = count_through > 3 ? nil: [NSError errorWithDomain:@"Domain" code:42 userInfo:nil];
    id        result       = nil;
    id        connection   = nil;
    
    count_through++;
    // API I'm mocking out here calls completions on main Q
    dispatch_async(dispatch_get_main_queue(),^{
        completion(connection, result, error);
    });
}
@end

int main(int argc, const char * argv[])
{

    @autoreleasepool {
        
        dispatch_queue_t requestQ = dispatch_queue_create("requestQ", 0);
        
        Counter (^CounterBuilder)(int) = ^Counter(int max){
            return ^BOOL{
                static int retries  = 0;
                return     retries++ >= max ? YES : NO;
            };
        };
        
        int (^backOffLinear)() = ^int{
            static int delay = 0;
            return     delay++;
        };
        
        RequestWrapperComp (^RequestWrapperBuilderComp)(id, CompletionHandler) = (
            ^RequestWrapperComp(id obj, CompletionHandler ch){
                return ^void{
                    [SMRequestFoo
                        request   : obj
                        completion: ch
                    ];
                };
            }
        );
        
        __block RequestWrapperComp reqcomp              = nil;
        __block Counter            retry_count_exceeded = nil;
        
        __block CompletionHandler  completion_handler   = (
            ^(id connection, id result, NSError * error)
            {
                if (error) {
                    if( retry_count_exceeded() ) {
                        NSLog(@"Failed at max retries, we're done here");
                    }
                    else {
                        NSLog(@"Retry...");
                        // Get off the main Q
                        dispatch_async( requestQ, ^{
                            sleep( backOffLinear() ); // hmmmmm...
                            reqcomp();
                        });
                    }
                }
                else { NSLog(@"OK all good now, moving on for other things"); }
            }
        );
            
        reqcomp              = RequestWrapperBuilderComp(nil, completion_handler);
        retry_count_exceeded = CounterBuilder(4);
        
        reqcomp();


        // Keep on truckin'
        [[NSRunLoop currentRunLoop] run];
    }
    return 0;
}


/* **
2014-06-26 10:10:19.302 completion_retry_spike_1[5167:303] Retry...
2014-06-26 10:10:19.304 completion_retry_spike_1[5167:303] Retry...
2014-06-26 10:10:20.305 completion_retry_spike_1[5167:303] Retry...
2014-06-26 10:10:22.307 completion_retry_spike_1[5167:303] Retry...
2014-06-26 10:10:25.309 completion_retry_spike_1[5167:303] OK all good now, moving on for other things
**  */