NSNotification in Background thread - iOS

Question

I am working on chat application in which messages are received in delegate method. From delegate method, I am calling NSNotification to update the messages in UI.

//Delegate method

- (void)didReceiveMessage:(XMPPMessage *)message{
     [[NSNotificationCenter defaultCenter]postNotificationName:@"MessageReceived"  object:nil userInfo:@{@"message":message}];
}

The above delegate method will be called for every new message that i receive. Suppose If i receive the large number of messages simultaneously, it cause UI to hang. If i add a background thread for a notification, then it will create a new thread for every delegate method call. It is not a good solution. How can i handle this scenario?

Answer 1

Instead of posting a notification after receiving a message you can directly send message to ViewController responsible for updating UI. For example

- (void)didReceiveMessage:(XMPPMessage *)message{
    MessageListController *messageListController; //get reference as per your UI implementation
    [messageListController updateUIWithMessage:message];
}

and in updateUIWithMessage method you can write optimised code to update your UI.

Answer 2

You should use NSOperationQueue and make it global (class level). Add NSOperations to it.

You can use maxConcurrentOperationCount property to set the no of max concurrent operations. In this way you can control the multiple operations coming at once. But for you case I think

maxConcurrentOperationCount = 1;

is good. Since you need messages to change the UI one by one. Or set it according to your need.