Observer pattern-The subject keeps track of the items to be observed by the observer

Aquarius_Girl · 05-02-2012, 07:10 AM

Observer pattern-
Assumption:

Out of the 10 items, the observer only wants to be subscribed to 3.
Subject calls a function of the observer to let him know that there are some updates.

Now, is it subject's responsibility to send the updates pertaining to only 3 items to the observer?
OR
Subject can simply tell the observer that there are updates - go and fetch whichever you want out of 10?

Which is the correct way out? Does it matter?

danielbmartin · 05-02-2012, 08:51 AM

Quote:

Originally Posted by Anisha Kaul

Observer pattern-
Assumption:

Out of the 10 items, the observer only wants to be subscribed to 3.
Subject calls a function of the observer to let him know that there are some updates.

Now, is it subject's responsibility to send the updates pertaining to only 3 items to the observer?
OR
Subject can simply tell the observer that there are updates - go and fetch whichever you want out of 10?

Which is the correct way out? Does it matter?

There is no right answer.

The most appropriate action is to fulfill whatever the observer was promised at the time he/she subscribed.

Daniel B. Martin

dugan · 05-02-2012, 08:53 AM

Either let the observer choose which items to subscribe to, or send all 10 item updates to the observer. Which one is "best" depends on which will ultimately give you simpler code. (And probably on the nature of the data being passed).