Tuesday, May 24, 2016

MVC-N: Isolating Network Calls From View Controllers

Marcus Zarra:

We have a network controller: it talks to the internet, your local network, or even be a flat file system. It then pushes data into your cache, into your persistence engine. Here comes the exciting part: your entire view layer talks to the cache only. It does not get data from the internet directly. The ViewController’s job is to display or update that data, not to do networking code. This design will serve you forever, and it has so many benefits that you’ll never want to use the anti-pattern ever again.


We can use the concurrent design of the NSOperation to do our network requests. In Swift, because we cannot access the property directly for finished, we have to do hacking (which I do have a radar for, and I am hoping they will fix this). The idea behind this overrided var is that we need to tell the queue that we are done. To do that, the queue is listening for “isFinished”. In Objective-C, isFinished translates into the variable Finished fine; in Swift, it only listens for “isFinished”, it does not listen for the actual property of Finish, you cannot change it.

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