uitableview - iOS- Update UITableViewCell information without reloading the row? -

let's have uitableview displays list of file metadata, , want show download_progress of each file in uilabel of custom uitableviewcell. (this arbitrarily long list - dynamic cells reused).

if want update label without calling either reloaddata or reloadrowsatindexpaths, how can it?

for wondering - don't want call either of reload... methods because there's no need reload entire cell each percentage point update on download_progress.

the solutions i've come across are:

• adding cell key-value observer file's download_progress.

• calling cellforrowatindexpath... directly obtain label , change it's text.

however, kvo in general isn't fun api work - , less when add cell reuse mix. calling cellforrowatindexpath directly each time percentage point added feels dirty though.

so, possible solutions? appreciated.

thanks.

as corollary doug's response, here ended going with:

each file has unique identifier, made responsible posting notifications updates attributes (think kvo, without hassle):

i made filenotificationtype enum (i.e. filenotificationtypedownloadtriggered, , filenotificationtypedownloadprogress). send progress nsnotification's userinfo nsdictionary along filenotificationtype.

- (void)postnotificationwithtype:(filenotificationtype)type andattributes:(nsdictionary *)attributes {     nsstring *unique_notification_id = <file unique id>;      nsmutabledictionary *mutable_attributes = [nsmutabledictionary dictionarywithdictionary:attributes];     [mutable_attributes setobject:@(type) forkey:@"type"];      nsdictionary *user_info = [nsdictionary dictionarywithdictionary:mutable_attributes];      dispatch_async(dispatch_get_main_queue(), ^{     [[nsnotificationcenter defaultcenter] postnotificationname:unique_notification_id object:nil userinfo:user_info];     }); } 

the file object has method enumerate types of notifications send:

- (nsarray *)notificationidentifiers {     nsstring *progress_id = <file unique id + filenotificationtype>;     nsstring *status_id = <file unique id + filenotificationtype>     nsstring *triggered_id = <file unique id + filenotificationtype>      nsarray *identifiers = @[progress_id, status_id, triggered_id];     return identifiers; } 

so when update attribute of file elsewhere, this:

nsdictionary *attributes = @{@"download_progress" : @(<progress_integer>)}; [file_instance postnotificationwithtype:filenotificationtypedownloadprogress andattributes:attributes]; 

on receiving end, table view delegate implemented these methods add / remove custom uitableviewcells observers these notifications:

- (void)tableview:(uitableview *)tableview willdisplaycell:(uitableviewcell *)cell forrowatindexpath:(nsindexpath *)indexpath {     file *file = [modelobject getfileatindex:indexpath.row];     (nsstring *notification_id in file.notificationidentifiers)     {         [[nsnotificationcenter defaultcenter] addobserver:cell selector:@selector(receivefilenotification:) name:notification_id object:nil];     } }  - (void)tableview:(uitableview *)tableview didenddisplayingcell:(uitableviewcell *)cell forrowatindexpath:(nsindexpath *)indexpath {     [[nsnotificationcenter defaultcenter] removeobserver:cell]; } 

finally, custom uitableviewcell has implement receivefilenotification: method:

 - (void)receivefilenotification:(nsnotification *)notification {     filenotificationtype type = (filenotificationtype)[notification.userinfo[@"type"] integervalue];      // access updated property info with: [notification.userinfo valueforkey:@"<your key here>"]      switch (type)     {         case filenotificationtypedownloadprogress:         {             // progress             break;         }         case filenotificationtypedownloadstatus:         {             // status             break;         }         case fsepisodenotificationtypedownloadtriggered:         {             // if download triggered             break;         }         default:             break;     } } 

hopefully helps looking update tableview cells without having reload them! benefit on key-value observing won't issues if file object deallocated cell still observing. don't have call cellforrow....

enjoy!