Does Option #1 below run some sort of implied queue? It does not seem to run on the main queue because when I tried to update UI stuff there it complained until I moved to Option #3 so I’m assuming that blocks have their own queue or thread? Before it complained I was under the impression if I didn’t start a dispatch queue that things would just run like normal, which in my mind would be on the main queue. Here’s some example code to illustrate:
// UserViewController.h
@interface UserViewController : NSObject
@property(nonatomic, strong) Server *server;
@property(nonatomic, strong) User *user;
@end
// UserViewController.m - Controller that sets a block for use in another class
@implementation UserViewController
- (void)doSomething {
// I'd like to call other methods and set @properties from the controller and I've heard
// __weak is the correct keyword to use (rather than __block or __strong).
__weak UserViewController *weakController = self;
// Option #0 - Outside of block
weakController.user = [[RHZUser alloc] init];
server.callbackBlock = ^(NSURLResponse *response, NSData *data, NSError *error) {
// Option #1 - Outside of dispatch queues. Is this in some sort of default queue?
weakController.user = [[RHZUser alloc] init];
dispatch_queue_t backgroundQueue
= dispatch_queue_create("com.example.backgroundQueue", nil);
dispatch_async(backgroundQueue, ^{
// Option #2 - This is on the serial queue I created
weakController.user = [[RHZUser alloc] init];
dispatch_async(dispatch_get_main_queue(), ^{
// Option #3 - The main queue where all my UI is
weakController.user = [[RHZUser alloc] init];
} // dispatch_async
} // dispatch_async
}; // self.callbackBlock
}
@end
// Server.m - Class that uses the block defined in the controller
@implementation Server
- makeAServerCall {
[NSURLConnection sendAsynchronousRequest:
[NSMutableURLRequest requestWithURL:restServiceURL]
queue:[[NSOperationQueue alloc] init]
completionHandler:self.callbackBlock];
}
@end
