IOS: Apple Push Notifications understanding - ios

Question

Four questions about Push Notifications.
-(void)application:(UIApplication *)application didReceiveRemoteNotification:(NSDictionary *)userInfo
{
UIApplicationState state = [application applicationState];
if (state == UIApplicationStateActive) {
//app is in foreground I can fetch
} else {
//App is in background, can I still fetch the server? Is there a time limit?
}
}
Using the code above, when the app is in background, can I still fetch the server? Is there a time limit? If the answer is: No, I cannot fetch the server in the background, are there alternatives?
Is there any other benefit of using silent notification besides triggering some method to run within 30 seconds when the app is in the background?
If using silent notification and the app is in the foreground, is the following method still called?
-(void)application:(UIApplication *)application didReceiveRemoteNotification:(NSDictionary *)userInfo fetchCompletionHandler:(void (^)(UIBackgroundFetchResult))completionHandler
{
completionHandler(UIBackgroundFetchResultNewData);
}
In the payload does "content-available" : 1 calls the method in Q3 (above)? or is there anything else that can trigger the method in Q3?

Answer 1

Yes you can still fetch the server when the app is in background. For many apps, the background state is just a brief stop on the way to the app being suspended.
No this is the main benefit of using silent notification see this link.
Yes application:didReceiveRemoteNotification:fetchCompletionHandler: is called regardless of app state.If app is suspended or not running, then the system wakes up or launches your app and puts it into the background running state before calling the method.
This method is intended for showing the updated content to the user.When this method is called, your app has up to 30 seconds of wall-clock time to perform the download operation and call the specified completion handler block. If the handler is not called in time, your app will be suspended.
Yes it calls application:didReceiveRemoteNotification:fetchCompletionHandler:, If you want a push notification to wake your app up in the background you need to enable the Remote Notifications capability and then implement the code to handle that remote notification (either by detecting it in the application:didFinishLaunchingWithOptions: if your app is not already running, or by implementing application:didReceiveRemoteNotification:fetchCompletionHandler: in the case your app is already running). In response to the remote notificaiton you would internally trigger your fetching code. Of course you also need to be doing registering for the remote notifications and sending the token to your server. please see this discussion