How to unsubscribe an iOS Device from an amazon SNS topic? - ios

Question

I'm developing an iOS application with Simple Notification Service (SNS) from Amazon Web Services. At this point the app registers the device to a Topic and can receive push notifications, which are published to the Topic. It is possible to subscribe a device to many Topics.
Now I'm trying to unsubscribe a device from a specific Topic, but the SNSUnsubscribeRequest needs a SubscriptionARN. I've tried to use the EndpointARN from the device, but it seems I've to use an extra SubscriptionARN for the combination of EndpointARN and TopicARN. How do I get this ARN?
In this post: How do you get the arn of a subscription? they ask for the whole list of subscribers and compare each EndpointARN with the EndpointARN of the device. This cant be the right way i think.
Subscribe to Topic
// Check if endpoint exist
if (endpointARN == nil) {
dispatch_async(dispatch_get_main_queue(), ^{
[[self universalAlertsWithTitle:#"endpointARN not found!" andMessage:#"Please create an endpoint for this device before subscribe to topic"] show];
});
return NO;
}
// Create topic if not exist
NSString *topicARN = [self findTopicARNFor:topic];
if (!topicARN) {
[self createTopic:topic];
topicARN = [self findTopicARNFor:topic];
}
// Subscribe to topic if exist
if (topicARN) {
SNSSubscribeRequest *subscribeRequest = [[SNSSubscribeRequest alloc] initWithTopicArn:topicARN andProtocol:#"application" andEndpoint:endpointARN];
SNSSubscribeResponse *subscribeResponse = [snsClient subscribe:subscribeRequest];
if (subscribeResponse.error != nil) {
NSLog(#"Error: %#", subscribeResponse.error);
dispatch_async(dispatch_get_main_queue(), ^{
[[self universalAlertsWithTitle:#"Subscription Error" andMessage:subscribeResponse.error.userInfo.description] show];
});
return NO;
}
}
return YES;
The method findTopicARNForTopic already iterates over the list of Topics and compare the suffix with the topic name. I really don't know if this is the best practice.
Unsubscribe from Topic
NSString *topicARN = [self findTopicARNFor:topic];
if (topicARN) {
SNSUnsubscribeRequest *unsubscribeRequest = [[SNSUnsubscribeRequest alloc] initWithSubscriptionArn:topicARN];
SNSUnsubscribeResponse *unsubscribeResponse = [snsClient unsubscribe:unsubscribeRequest];
if (unsubscribeResponse.error) {
NSLog(#"Error: %#", unsubscribeResponse.error);
}
}

Answer 1

For now I ask for the whole subscriber list and compare the EndpointARN with the EndpointARN of the Device. With the following method i get the subscription arn:
- (NSString *)findSubscriptionARNForTopicARN:(NSString *)topicARN
{
// Iterate over each subscription arn list for a topic arn
NSString *nextToken = nil;
do {
SNSListSubscriptionsByTopicRequest *listSubscriptionRequest = [[SNSListSubscriptionsByTopicRequest alloc] initWithTopicArn:topicARN];
SNSListSubscriptionsByTopicResponse *response = [snsClient listSubscriptionsByTopic:listSubscriptionRequest];
if (response.error) {
NSLog(#"Error: %#", response.error);
return nil;
}
// Compare endpoint arn of subscription arn with endpoint arn of this device
for (SNSSubscription *subscription in response.subscriptions) {
if ([subscription.endpoint isEqualToString:endpointARN]) {
return subscription.subscriptionArn;
}
}
nextToken = response.nextToken;
} while (nextToken != nil);
return nil;
}
and with this method i remove the device from a topic:
- (void)unsubscribeDeviceFromTopic:(NSString *)topic
{
NSString *subscriptionARN = [self findSubscriptionARNForTopic:topic];
if (subscriptionARN) {
SNSUnsubscribeRequest *unsubscribeRequest = [[SNSUnsubscribeRequest alloc] initWithSubscriptionArn:subscriptionARN];
SNSUnsubscribeResponse *unsubscribeResponse = [snsClient unsubscribe:unsubscribeRequest];
if (unsubscribeResponse.error) {
NSLog(#"Error: %#", unsubscribeResponse.error);
}
}
}

Answer 2

You could also store the SubscriptionArn in the SubscribeResponse and use this value in the UnSubscribeRequest.