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POXcode - Is this MVC?
 

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    <p>I'm a part-time notepad website coder taking steps into IOS apps. I got my first mac last week and have cobbled together a half working app. Now, convinced by this <a href="https://stackoverflow.com/a/2443020/781200">SO answer</a>, I am restarting trying to learn MVC. I am on a very steep learning curve so please bear with me.</p> <p>I have read up on MVC, separation of layers, three boxes and some arrows, I get it. However, translating the theory into the real world is frustrating. Most example apps I have looked at do not seem to use MVC. Even this <a href="http://developer.apple.com/library/ios/#samplecode/LazyTableImages/Introduction/Intro.html" rel="nofollow noreferrer">LazyTableImages example</a> from Apple seems to use <code>app delegate</code> as the model which confuses me. I have built on this excellently <a href="http://fromideatoapp.com/downloads/example/" rel="nofollow noreferrer">simple MVC example</a>.</p> <p>My app retrieves location markers from a web service. I have a tabbed application using ARC. One tab has a Mapkit map to display the markers.</p> <p>A simple class to hold a marker record:</p> <pre><code>@interface MarkerRecord : NSObject @property (strong, nonatomic) NSDecimalNumber *lat; @property (strong, nonatomic) NSDecimalNumber *lon; @property (strong, nonatomic) NSString *des; </code></pre> <p>A Model class, holding a collection of Marker classes, to serve both views. This is my Model class .h:</p> <pre><code>@interface MarkersModel : NSObject - (void)getMarkers; // Send HTTP GET to web service to retrieve JSON markers - (void)postMarker; // Send HTTP POST to web service to INSERT new marker record </code></pre> <p>And the implementation:</p> <pre><code>@interface MarkersModel () @property (strong, nonatomic) NSArray *data; @end @implementation MarkersModel @synthesize data; - (void)getMarkers { // Send HTTP GET to web service to retrieve JSON markers ... } - (void)objectLoader:(RKObjectLoader *)objectLoader didLoadObjects:(NSArray *)objects { // Thanks to Restkit data is an array of Marker classes data = objects; // Pass data to controller } </code></pre> <p>A mapViewController class .h:</p> <pre><code>#import &lt;MapKit/MapKit.h&gt; #import "MarkersModel.h" @interface MapViewController : UIViewController&lt;MKMapViewDelegate&gt; { MarkersModel *markersModel; } @property (nonatomic, strong) IBOutlet MKMapView *mapView; @end </code></pre> <p>And the implementation:</p> <pre><code>@interface MapViewController () @end @implementation MapViewController - (void)viewDidLoad { [super viewDidLoad]; // Create instance of markers model markersModel = [[MarkersModel alloc] init]; } -(void)viewWillAppear:(BOOL)animated { [markersModel getMarkers]; } - (void)putMarkersOnMap { // To be called by Markers Model ... } </code></pre> <p>Here's my main question:</p> <ul> <li>Is my code outline above (the beginnings of) a decent MVC implementation?</li> </ul> <p>If so:</p> <ul> <li>how do I get the Model to update the Controller ( i.e. how do I get MarkersModel.objectLoader function to call mapViewController.putMarkersOnMap)?</li> </ul> <p>I strongly suspect the answer is a custom delegate on the controller but I cannot for the life of me see how to implement it. I cannot relate any examples to my situation. I think I need something like this on the controller:</p> <pre><code>@class MapViewController; @protocol MapViewControllerDelegate; </code></pre> <p>While I am at it some additional questions:</p> <ul> <li>Will I create any dangling pointers - I suspect something should be <code>unsafe_unretained</code> (I am compiling to 4.3)?</li> <li>Is my MarkersModel declaration in the controller class correct? I am concerned that it will not be managed by ARC. I also suspect it is public but should be private.</li> <li>Should the MarkersModel.getMarkers method be static?</li> </ul> <p>I hope this is clear and an acceptable question. Thanks for your patience, Polly.</p>
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