ios - Does reloadData of Tableview execute immediately in this case -

i read [_tableview reloaddata] sends message main queue update , display data in table view. based on discuss following case. suppose method sends message main queue before [_tableview reloaddata] in case second message processed before [_tableview reloaddata] ?

now case

suppose have 2 threads ta , tb , have 2 methods methodaand methodb this

this methoda

- (void) methoda { dispatch_async(dispatch_get_main_queue(), ^{                     [myarray addobject:@"someobject"];                     ///----------<timeframea>----------------                     [_tableview reloaddata]                 }); } 

this methodb

- (void) methodb { dispatch_async(dispatch_get_main_queue(), ^{                     //runs under assumption "someobject" has been displayed in tableview                     //make changes tableview/                 }); } 

suppose methodb called threadb , occurs during timeframea. in case methodb called before [_tableview reloaddata] ? there way me make sure methodb runs when tableview displaying updated data ?

the main dispatch queue (which associated main thread) serial queue, not concurrent. therefore cannot happen in

dispatch_async(dispatch_get_main_queue(), ^{                     [myarray addobject:@"someobject"];                     ///----------<timeframea>----------------                     [_tableview reloaddata]                 }); } 

any other code executes on main queue between adding object , reloading table view.

any other block dispatched main queue executes either before or after block.