ios - Waiting for multiple blocks to finish -

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i have methods retrieve object information internet:

- (void)downloadappinfo:(void(^)())success                 failure:(void(^)(nserror *error))failure; - (void)getavailablehosts:(void(^)())success                   failure:(void(^)(nserror *error))failure; - (void)getavailableservices:(void(^)())success                      failure:(void(^)(nserror *error))failure; - (void)getavailableactions:(void(^)())success                     failure:(void(^)(nserror *error))failure;

the downloaded stuff gets stored in object properties, why success functions return nothing.

now, want have 1 method this: 

- (void)synceverything:(void(^)())success                failure:(void(^)(nserror *error))failure;

which nothing else calling methods above, , returning after every single method has performed success or failure block.

how can this?

hint: aware cascading methods calls in each others success block work. neither 'clean' nor helpful when later implementations include further methods.

edit:

i tried running each of calls in nsoperation , adding nsoperations nsoperationqueue followed "completion operation" depends on every 1 of preceding operations.

this won't work. since operations considered completed before respective success/failure blocks return.

i aware, put each of calls in subclassed nsoperation, can myself decide when fire completion block. sounds overkill, or way go?

this did:

nsoperation *completionoperation = [nsoperation new]; completionoperation.completionblock = sucess; // defined somewhere else  nsoperationqueue *queue = [nsoperationqueue new];  for(anappliance *appliance in _mutappliances) {     nslog(@"add app");      nsoperation *operation = [nsoperation new];      operation.completionblock =     ^{         [self downloadhostsforappliancewithname:appliance.networksettings.name                                         success:^          {              nslog(@"downloaded");              //sucess();          }                                         failure:^(nserror *error)          {              //failure(error);          }];     };       [completionoperation adddependency:operation];      [queue addoperation:operation]; }  [queue addoperation:completionoperation];

edit:

now tried dispatch_group thing. not me wether doing right way:

for(appliance *appliance in _mutappliances)         dispatch_group_async(group,                              dispatch_get_global_queue(dispatch_queue_priority_default, 0),                              ^ {                                  nslog(@"block start");                                   [appliance downloadappinfo:^                                   {                                       nslog(@"block success");                                   }                                                     failure:^(nserror *error)                                   {                                       nslog(@"block end");                                   }];                                   nslog(@"block end");                              });      dispatch_group_notify(group,                           dispatch_get_global_queue(dispatch_queue_priority_default, 0),                           ^ {                               nslog(@"final block");                               sucess();                           });

unfortunately, not working way. "block success" shows @ end.

you there, problem methods asynchronous, need synchronization step. try following fix:

for(appliance *appliance in _mutappliances) {   dispatch_group_async(      group,      dispatch_get_global_queue(dispatch_queue_priority_default, 0), ^{        dispatch_semaphore_t sem = dispatch_semaphore_create( 0 );         nslog(@"block start");         [appliance downloadappinfo:^{           nslog(@"block success");             dispatch_semaphore_signal(sem);        }        failure:^(nserror *error){          nslog(@"block failure");          dispatch_semaphore_signal(sem);        }];         dispatch_semaphore_wait(sem, dispatch_time_forever);         nslog(@"block end");  });   dispatch_group_notify(    group,    dispatch_get_global_queue(dispatch_queue_priority_default, 0),^{      nslog(@"final block");      success();  }); }

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