| [](https://www.versioneye.com/objective-c/reachability/references) |
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| # Reachability |
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| This is a drop-in replacement for Apple's `Reachability` class. It is ARC-compatible, and it uses the new GCD methods to notify of network interface changes. |
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| In addition to the standard `NSNotification`, it supports the use of blocks for when the network becomes reachable and unreachable. |
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| Finally, you can specify whether a WWAN connection is considered "reachable". |
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| *DO NOT OPEN BUGS UNTIL YOU HAVE TESTED ON DEVICE* |
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| ## Requirements |
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| Once you have added the `.h/m` files to your project, simply: |
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| * Go to the `Project->TARGETS->Build Phases->Link Binary With Libraries`. |
| * Press the plus in the lower left of the list. |
| * Add `SystemConfiguration.framework`. |
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| Boom, you're done. |
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| ## Examples |
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| ### Block Example |
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| This sample uses blocks to notify when the interface state has changed. The blocks will be called on a **BACKGROUND THREAD**, so you need to dispatch UI updates onto the main thread. |
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| // Allocate a reachability object |
| Reachability* reach = [Reachability reachabilityWithHostname:@"www.google.com"]; |
| |
| // Set the blocks |
| reach.reachableBlock = ^(Reachability*reach) |
| { |
| // keep in mind this is called on a background thread |
| // and if you are updating the UI it needs to happen |
| // on the main thread, like this: |
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| dispatch_async(dispatch_get_main_queue(), ^{ |
| NSLog(@"REACHABLE!"); |
| }); |
| }; |
| |
| reach.unreachableBlock = ^(Reachability*reach) |
| { |
| NSLog(@"UNREACHABLE!"); |
| }; |
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| // Start the notifier, which will cause the reachability object to retain itself! |
| [reach startNotifier]; |
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| ### `NSNotification` Example |
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| This sample will use `NSNotification`s to notify when the interface has changed. They will be delivered on the **MAIN THREAD**, so you *can* do UI updates from within the function. |
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| In addition, it asks the `Reachability` object to consider the WWAN (3G/EDGE/CDMA) as a non-reachable connection (you might use this if you are writing a video streaming app, for example, to save the user's data plan). |
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| // Allocate a reachability object |
| Reachability* reach = [Reachability reachabilityWithHostname:@"www.google.com"]; |
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| // Tell the reachability that we DON'T want to be reachable on 3G/EDGE/CDMA |
| reach.reachableOnWWAN = NO; |
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| // Here we set up a NSNotification observer. The Reachability that caused the notification |
| // is passed in the object parameter |
| [[NSNotificationCenter defaultCenter] addObserver:self |
| selector:@selector(reachabilityChanged:) |
| name:kReachabilityChangedNotification |
| object:nil]; |
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| [reach startNotifier]; |
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| ## Tell the world |
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| Head over to [Projects using Reachability](https://github.com/tonymillion/Reachability/wiki/Projects-using-Reachability) and add your project for "Maximum Wins!". |