Should I have all my web service code in my view controller

I have noticed that with iPhone programming you kind of need to retrieve your data from within the ViewController because of the way the data is retrieved.

e.g.: ViewDidLoad is called. You start retrieving the data and then when its finished a message is sent to your viewcontroller e.g. requestFinished and this is where you configure/refresh your UI.

The problem that I have with this approach is that I have a bunch of web service code and XML building and parsing all in my view controller.

Does anyone know if this is the correct approach or is there a better wa开发者_开发知识库y to do this.

In .NET I would have classes specifically for retrieving data from webservices and I would simply call the web service to fetch the data and I could use the same web service at various places inside my app.

There is no reason to do that different in Objective-C/Cocoa. You should create a class that handles the web service and notifies the view controller when data is available.

No, it absolutely isn't the correct approach. The key to this is the MVC paradigm, - model, view, controller - your data classes are perfectly suited to being the M = model so put all your data handling code inside a dedicated model class.

Because the url handling is hopefully asynchronous, your model will still need to inform your view controller when various events have taken place. You have a couple of choices here but the most appropriate is probably to use a delegate pattern so that the model can basically initiate a call back to the view controller when it has data that needs displaying etc.

(The other approach would be to use notifications which is less tightly coupled, and perfectly viable in this scenario, but delegates would be more appropriate).

Well you could create a parse that will parse your XML in a seprate class, and even your http request can be in a seprate class. There is no need to do every thing in the the on viewcontroller.

Just be sure to create delegate or use the notification center if you are using threads. Set the delegate on either the request or parse to nil if the view controller get unloaded.