AppPay | money_with_wings | SDK library

It's really not an error with the code I just want to know how to not have to refetch the data whenever the view loads again but I can provide it

The simple answer is to avoid fetching the data every time the view loads.

Using viewDidLoad() for setup work that's not related to the state of the views isn't a great practice because it means that work will be repeated unnecessarily whenever the controller's view hierarchy is loaded, which may happen more often than just when the controller is instantiated.

In your case, fetching the data you need could be done in the controller's initializer, or it could be done lazily in the getter for the payments data, e.g. if the payments array is nil, return an empty array and call loadData(). When the completion routine in that method gets called, it'll set the allPayments property, which in turn will set the payments property, which in turn will cause the table to reload. If you do things that way, you avoid loading the data unnecessarily; the data will persist as long as the same view controller is used.

But you can do better than that. Imagine that the shoe was on the other foot, and it's the child view controller, the one that you're transitioning to in you question, that keeps requesting data. In this case, that view controller might be created and destroyed each time you take some action (like tapping a row) in the Home view controller, so whatever data it contained is also lost and the controller is starting from scratch. If you tap the same row three times, do you really need to load the same data three times? Can we save the data somewhere outside the view controller, so that it remains available?

That's what a data model is for. This is the M in Model-View-Controller. A model is an object or graph of objects that manages your app's data and implements the app's "business logic" -- the operations on the data that have nothing to do with the user interface. If you were to reimplement your app as a command line program, or maybe a web service, what part of the code could you keep? That's the stuff that belongs in the model.

Your PaymentService looks a lot like a model: it stores the data you need, and it knows how to fetch the data that it doesn't already have. What if you move that class outside your view controller and let it exist on its own? Then your view controller would be freed from having to keep a copy of the data itself -- it could just refer to the model. And any transient view controllers like the child controller described above would just ask the model for the data they need; if the model has it already, it returns it, and if it doesn't, it fetches it. Instead of the Home controller passing data directly to a child controller, it could just provide a piece of the model.