Question

Explanation

My app basically uses a mapview with an overlay of polygons that represent buildings, coupled with an annotation. So for this it imports a custom class called Annotation that handles the popup details when the annotation is tapped, meaning it store the building’s name and address. At this time the callout (the blue disclosure button) loads an empty DetailViewController object (as there’s not really any data to pass through).

I soon added a new feature in the form of a searchable table that loads custom objects of the Building class (with similar properties to Annotation, plus images and more details) that then loads in the aforementioned DetailViewController class with the building’s details.

So to summarise, the MapVC contains multiple annotations, which when the relevant disclosure button is tapped open the DetailVC. SearchVC is accessed by a button on the MapVC and has a table of Building objects, which loads a DetailVC with the relevant data, like so:

Next Step

So now I want to implement functionality into the blue disclosure button on the callout, so when the user taps it it’ll load the building details. At the moment all it has is the annotation’s details. I could add the extra properties to the annotation to make it complete but I think it’s much better to just work with one custom class called Building, which has a MKAnnotation nature. Then this Building class is loaded for the annotations and searchVC’s table.

Question

So finally, what’s the best way to go around this? I want all the data to be stored independently of any of the VCs in the diagram. I followed a tutorial from Apple (the BirdSighting one) which uses a separate Datacontroller class, which I’d then load into other classes. Is this the best approach?

Answer 1

You’re talking about MVC, model-view-controller. This is a very smart way to handle things, and is a good practice to get into. The model stores the data, in this case, building names, etc. The view displays data. The controller is what connects the view to the model, updates the view, gets notifications from users and in turn updates the model.

I use a singleton pattern for model data. Only one instance of a singleton is ever present in an application. That way, the data is not bound to any one particular view controller. Data only gets updated in once place, the model. It’s a lot easier to trouble shoot issues with a singular point of convergence for application data objects.

I have a macro that I define in my PCH file.

#import "DataController.h"

#define DATA() [DataController sharedInstance]

In my code I can easily get to my model class by calling

DataController *data = DATA();

All of my views and viewcontrollers access objects stored in DataController, so there are never two view controllers handling separate pieces of information independently. All references point to the same place.

Some people use the AppDelegate object to store data, but it can quickly turn into a 1000 line beast. I prefer to keep the AppDelegate clean 🙂