为什么收到推送通知时我的iOS应用程序崩溃？

Question

My iOS app is crashing when it receives a push notification message while running. I'm using the sandbox APNS environment, and using Amazon SNS to send the APNS messages.

When debugging, I set a breakpoint on the first line of the following code snippet:

- (void)application:(UIApplication *)application didReceiveRemoteNotification:(NSDictionary *)userInfo
{
  NSDictionary *apnsPayload = [NSDictionary dictionaryWithDictionary:userInfo];

When the app receives a push notification, it hits the breakpoint and lets me debug; at this point I can see that userInfo is non-nil and contains the expected dictionary.

However, when I step through the code, the app crashes with EXC_BAD_ACCESS at the very next line—the assignment to apnsPayload . It seems like userInfo might be getting deallocated prematurely, but I'm not sure why, or more importantly how to change this.

Answer 1

I don't think it makes sense to turn the NSDictionary into another NSDictionary with [NSDictionary dictionaryWithDictionary:] ... also NSDictionary can be non-nil but contain 0 key entries (an empty dictionary).

Perhaps you want: NSDictionary *apnsPayload = [userInfo objectForKey: @"alert"]; ?

See: https://developer.apple.com/library/ios/documentation/NetworkingInternet/Conceptual/RemoteNotificationsPG/Chapters/ApplePushService.html

Answer 2

Well, I've still no idea why this is happening, but it stops when I NSLog() the userInfo argument first. Adding the following line as the first line of the function prevents the crash:

  NSLog(@"Received APNS with userInfo %@", userInfo);

I can then assign using - [userInfo objectForKey:] without causing a crash. (To be clear, attempting this same assignment without the prior NSLog() results in the EXC_BAD_ACCESS crash.)