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well, that means that function can be assigned to variables, constants and also can be passed as arguments, very cool right?btw, they are called blocks in objective-C and I must accept that the syntax to create one in that language, although I declared myself many times as a big Objective — C fan, is more than horrifying. well, in this function the T becomes of type [String: Any Object], can you see how awesome generics are, not yet?It is also said that the closure argument the function body.Inside this new function, we are going to use the class URLSession to get data from a web server, before we continue I suggest to check Networking libraries like Alamofire or Tron, to handle networking calls, they definitely will make your life easier, but at this time I won’t use them because I don’t want to go to deep in how to include them in your project using cocoapods.(maybe I’ll do another tutorial in the future doing that :) )Copy this inside the function.Making a request to a server can give us different kind of errors and it will be nice to know more about them, not only to make our debugging easier but also to tell the user the type of issue that he/she is experimenting.At this point, we are handling errors just by making the program returns and that’s fine but we can do it better, if you see the enum, it has two cases, a Success, that we already used, and one case Errors.Do you remember when you are under a tunnel or camping with friends, and the content from a feed of an app that you are using becomes just a blank screen?It would not be better if we as developers find a way to show some content to the user in those situations and make her/him have a better experience?
In order to keep our code clean we are going to separate the Core Data implementation from the App Delegate, you can just keep it like it is and make a reference every time to your App Delegate when you need to, but a better way to do it is to create a different class to separate responsibilities, create a new file subclass of NSObject and name it Core Data Stack.At this point you are probably asking, so…what is the enum for?and I a glad you asked (Hope you did : P ), well, I am going to show you one way to handle errors.Closures are great to handle Asynchronous calls because they are executed after the completion of a certain task, that’s why sometimes are named as completion handlers. ..it’s ok, just get the idea that you don’t need to create a specific enum for every type thank to generics. the definition is actually very simple and easy to understand.If a closure is passed as an argument to a function and it is invoked after the function returns, the closure is escaping.
So, how do we fix this issue and make content available, somehow, even in situations with a poor internet connection?