Archiving and Unarchiving data/model objects - objective-c

Question

I'm following the MVCS paradigm for saving and then loading instances of data objects in a Test app related to updating mapping data.
BNRMapPoint.h
#import <Foundation/Foundation.h>
#import <MapKit/MapKit.h>
#import <CoreLocation/CoreLocation.h>
#interface BNRMapPoint : NSObject<MKAnnotation, NSCoding>
{
double latitude;
double longitude;
#public NSArray *mapPoints;
}
-(id) initWithCoordinate:(CLLocationCoordinate2D)c title:(NSString *)t subTitle:(NSString *)st;
//this is required property in MKAnnotation Protocol
#property (nonatomic, readonly) CLLocationCoordinate2D coordinate;
//this is an optional property in MKAnnotation Protocol
#property (nonatomic, copy) NSString *title;
//this is an optional property in MKAnnotation Protocol
#property (nonatomic,readonly,copy) NSString *subTitle;
#end
BNRMapPoint.m (Model)
#import "BNRMapPoint.h"
#implementation BNRMapPoint
#synthesize coordinate=_coordinate;
#synthesize title=_title;
#synthesize subtitle=_subtitle;
-(void)encodeWithCoder:(NSCoder *)aCoder{
latitude = self.coordinate.latitude;
longitude = self.coordinate.longitude;
[aCoder encodeObject:self.title forKey:#"title"];
[aCoder encodeObject:_subTitle forKey:#"subTitle"];
[aCoder encodeDouble: latitude forKey:#"latitude"];
[aCoder encodeDouble:longitude forKey:#"longitude"];
}
-(id)initWithCoder:(NSCoder *)aDecoder{
if (self= [super init]) {
[self setTitle:[aDecoder decodeObjectForKey:#"title"]];
self->_subTitle= [aDecoder decodeObjectForKey:#"subTitle"];
latitude= [aDecoder decodeDoubleForKey:#"latitude"];
longitude= [aDecoder decodeDoubleForKey:#"longitude"];
}
return self;
}
-(id)initWithCoordinate:(CLLocationCoordinate2D)c title:(NSString *)t subTitle:(NSString *)st{
if (self= [super init]) {
self.coordinate=c;
self.title=t;
_subtitle=st;
}
return self;
}
-(id) init{
return [self initWithCoordinate:CLLocationCoordinate2DMake(43.07, -89.32) title:#"Hometown" subTitle:self.subtitle];
}
#end
WhereamiViewController.h
#import <UIKit/UIKit.h>
#import <CoreLocation/CoreLocation.h>
#import <MapKit/MapKit.h>
#import "BNRMapPoint.h"
#import "RootObject.h"
#interface WhereamiViewController : UIViewController<CLLocationManagerDelegate,MKMapViewDelegate,UITextFieldDelegate>
{
#public RootObject *rootObj;
CLLocationManager *locationManager;
IBOutlet MKMapView *worldView;
IBOutlet UIActivityIndicatorView *activityIndicator;
IBOutlet UITextField *locationTitleField;
}
-(IBAction)buttonDidGetPressed:(id)sender;
-(BOOL)textFieldShouldReturn:(UITextField *)textField;
-(void)findLocation;
-(void)foundLocation:(CLLocation *)loc;
#end
WhereamiViewController.m (ViewController)
#import "WhereamiViewController.h"
#interface WhereamiViewController ()
#end
#implementation WhereamiViewController
-(IBAction)buttonDidGetPressed:(UISegmentedControl *)sender{//Silver challenge
NSLog(#"%#",NSStringFromSelector(_cmd));
if([sender selectedSegmentIndex]==0){
[worldView setMapType:MKMapTypeStandard];
}
else if([sender selectedSegmentIndex]==1){
[worldView setMapType:MKMapTypeHybrid];
}
else if([sender selectedSegmentIndex]==2){
[worldView setMapType:MKMapTypeSatellite];
}
}
-(id)initWithNibName:(NSString *)nibNameOrNil bundle:(NSBundle *)nibBundleOrNil{
NSLog(#"%#", NSStringFromSelector(_cmd));
if (self=[super initWithNibName:nibNameOrNil bundle:nibBundleOrNil]) {
rootObj= [[RootObject alloc] init];
locationManager= [[CLLocationManager alloc] init];
[locationManager setDelegate:self];//self is Whereamicontroller. The delegate pointer is of type id<CLLocationManagerDelegate> and is an ivar of CLLocationManager.
[locationManager setDesiredAccuracy:kCLLocationAccuracyBest];
}
NSLog(#"test");
return self;
}
-(void) viewDidLoad{
// [worldView setMapType:MKMapTypeSatellite]; Bronze challenge
[worldView setShowsUserLocation:YES];
}
-(void)findLocation{
NSLog(#"%#",NSStringFromSelector(_cmd));
[locationManager startUpdatingLocation];//This calls locationManager:didUpdateLocations:
NSLog(#"location updated");
[activityIndicator startAnimating];
[locationTitleField setHidden:YES];
}
-(BOOL)textFieldShouldReturn:(UITextField *)textField{
NSLog(#"%#",NSStringFromSelector(_cmd));
[self findLocation];
[textField resignFirstResponder];
return YES;
}
-(void)mapView:(MKMapView *)mapView didUpdateUserLocation:(MKUserLocation *)userLocation{
NSLog(#"%#",NSStringFromSelector(_cmd));
CLLocationCoordinate2D centerCoordinate= [[userLocation location] coordinate]; //get the coordinate of current location.
MKCoordinateSpan span= MKCoordinateSpanMake(250, 250);//Structure members
MKCoordinateRegion mapPortionToDisplay= MKCoordinateRegionMakeWithDistance(centerCoordinate, span.latitudeDelta, span.longitudeDelta);//span.latitudeDelta=250 and span.longitudeDelta=250
[worldView setRegion:mapPortionToDisplay animated:YES];
// [worldView setRegion:mapPortionToDisplay];
}
-(void)locationManager:(CLLocationManager *)manager didUpdateHeading:(CLHeading *)newHeading{
NSLog(#"%#",NSStringFromSelector(_cmd));
NSLog(#"Heading %#",newHeading);
}
-(void)foundLocation:(CLLocation *)loc{
NSLog(#"%#",NSStringFromSelector(_cmd));
CLLocationCoordinate2D coord= [loc coordinate];
NSDateFormatter *formatter= [[NSDateFormatter alloc] init];
NSDate *currentDate= [[NSDate alloc] init];
[formatter setDefaultDate:currentDate];
BNRMapPoint *bmp= [[BNRMapPoint alloc] initWithCoordinate:coord title:[locationTitleField text] subTitle:[[formatter defaultDate] description]];
[rootObj.mapPoints addObject:bmp];
[worldView addAnnotation:bmp];
MKCoordinateRegion region= MKCoordinateRegionMakeWithDistance(coord,250,250);
[worldView setRegion:region animated:YES];
//RESET the UI
[locationTitleField setText:#" "];
[activityIndicator stopAnimating];
[locationTitleField setHidden:NO];
[locationManager stopUpdatingLocation];
}
-(void)locationManager:(CLLocationManager *)manager didUpdateLocations:(NSArray *)locations{ //CLLocationManagerDelegate method implementation
NSLog(#"%#", NSStringFromSelector(_cmd));
// NSTimeInterval t0=[[locations lastObject] timeIntervalSinceNow];
NSLog(#"%#",(CLLocation *)[locations lastObject]);
NSTimeInterval t= [[(CLLocation *)[locations lastObject] timestamp] timeIntervalSinceNow];
if (t<-180) {
return; //No op
}
[self foundLocation:[locations lastObject]];
}
-(void)locationManager:(CLLocationManager *)manager didFailWithError:(NSError *)error{
NSLog(#"Could not find location: %#",error);//CLLocationManagerDelegate method implementation
}
#end
RootObject.h
#import <Foundation/Foundation.h>
#interface RootObject : NSObject
#property NSMutableArray *mapPoints;
-(BOOL)saveChanges;
-(NSString *)dataObjectArchivePath;
#end
RootObject.m (Store)
#import "RootObject.h"
#implementation RootObject
#synthesize mapPoints;
-(NSString *)dataObjectArchivePath{
NSArray *documentDirectories= NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
NSString *documentDirectory= [documentDirectories objectAtIndex:0];
NSString *finalPath= [documentDirectory stringByAppendingPathComponent:#"items.archive"];
return finalPath;
}
-(BOOL)saveChanges{
NSString *path= [self dataObjectArchivePath];
return [NSKeyedArchiver archiveRootObject:self.mapPoints toFile:path];writing to the file items.archive
}
-(id)init{
if (self=[super init]) {
NSString *path= [self dataObjectArchivePath];
self.mapPoints= [NSKeyedUnarchiver unarchiveObjectWithFile:path];//reading from the file items.archive
if (!self.mapPoints) {
self.mapPoints= [[NSMutableArray alloc] init];
}
}
return self;
}
#end
AppDelegate.m
- (void)applicationDidEnterBackground:(UIApplication *)application
{
// Use this method to release shared resources, save user data, invalidate timers, and store enough application state information to restore your application to its current state in case it is terminated later.
// If your application supports background execution, this method is called instead of applicationWillTerminate: when the user quits.
NSLog(#"%#",NSStringFromSelector(_cmd));
BOOL success= [[BNRItemStore sharedStore] saveChanges];
if (success) {
NSLog(#"Saved all of the BNRItems");
}
else{
NSLog(#"Could not save any of the BNRItems");
}
}
In the above code, the saveChanges method is called from application: didEnterBackground:. So i haven't made a singleton object for the Store (RootObject). But i instantiated it in the designated initializer of viewController. The data to be archived is BNRMapPoint objects. On the entering background state, the code did save the objects successfully. However after the relaunching the app, the initWithCoder is where its getting stuck. The app crashes when it comes to reading the previously saved MapPoint objects. Pls help.. I've checked almost possible. Don't know what to do. I'm stuck.

Answer 1

So the problem is that you have:
#property (nonatomic, readonly) CLLocationCoordinate2D coordinate;
And you are trying to use setter on read only property:
self.coordinate=c;
This is why it says that unrecognized selector is send - becuase it's readonly so setter doesn't exists. Using property this was is the same as calling:
[self setCoordinate:c]
Just make property assignable