12.7. Handling Network Connections in the Background
Problem
You are using instances of NSURLConnection
to
send and receive data to and from a web server and are wondering how
you can allow your application to work in the multitasking environment
of iOS without connection failures.
Solution
Make sure you support connection failures in the block objects that you submit to your connection objects.
Discussion
For applications that use NSURLConnection
but do not borrow extra time
from iOS when they are sent to the background, connection handling is
truly simple. Let’s go through an example to see how an asynchronous
connection will act if the application is sent to the background and
brought to the foreground again. For this, let’s send an asynchronous
connection request to retrieve the contents of a URL (say, Apple’s
home page):
- (BOOL) application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions{ NSString *urlAsString = @"http://www.apple.com"; NSURL *url = [NSURL URLWithString:urlAsString]; NSURLRequest *urlRequest = [NSURLRequest requestWithURL:url]; NSOperationQueue *queue = [[NSOperationQueue alloc] init]; [NSURLConnection sendAsynchronousRequest:urlRequest queue:queue completionHandler:^(NSURLResponse *response, NSData *data, NSError *error) { if ([data length] > 0 && error != nil){ /* Date did come back */ } else if ([data length] == 0 && error != nil){ /* No data came back */ } else if (error != nil){ /* Error happened. Make sure you handle ...
Get iOS 5 Programming Cookbook now with the O’Reilly learning platform.
O’Reilly members experience books, live events, courses curated by job role, and more from O’Reilly and nearly 200 top publishers.