MKMapKit - EXC_BAD_ACCESS when looping through MKAnnotations

Question

I've been stuck on this EXC_BAD_ACCESS error 2 days now. I have a reloadAnnotations method that removes all annotations before adding new annotations. Before removing the annotation this method should be checking to see if the new set contains the same location so it's not removed and re-added. But as soon as I try to trace out the current annotation title I get this error Thread 1: Program received signal: "EXC_BAD_ACCESS"

And when I view the annotation in the debugger the title property says "Invalid Summary". It must be caused by a value not being retained but I've tried everything and can't figure it out.

Why can't I log the annotation title to NSLog?

And why can't I compare each title and coords to other objects?

BrowseController.m

-(void)reloadAnnotations
{
    NSMutableArray *toRemove = [NSMutableArray arrayWithCapacity:10];
    for (id annotation in _mapView.annotations) {
        if (annotation != _mapView.userLocation) {
            //ParkAnnotation *pa = (ParkAnnotation *)annotation;
            ParkAnnotation *pa = annotation;
            NSLog(@"pa.title %@", pa.title); // Thread 1: Program received signal: "EXC_BAD_ACCESS"
            [toRemove addObject:annotation];
        }
    }
    // DON'T REMOVE IT IF IT'S ALREADY ON THE MAP!!!!!! 
    for(RKLocation *loc in locations) 
    {
        CLLocationCoordinate2D location;
        location.latitude = (double)[loc.lat doubleValue];
        location.longitude = (double)[loc.lng doubleValue];
        ParkAnnotation *parkAnnotation = [[ParkAnnotation alloc] initWithTitle:loc.name andCoordinate:location];      
        [_mapView addAnnotation:parkAnnotation];
    }
    [_mapView removeAnnotations:toRemove];
}



- (MKAnnotationView *)mapView:(MKMapView *)map viewForAnnotation:(id <MKAnnotation>)annotation
{
    NSLog(@"BrowseViewController map viewForAnnotation");
    MKPinAnnotationView *pin = (MKPinAnnotationView *)[_mapView dequeueReusableAnnotationViewWithIdentifier: @"anIdentifier"];

    if (pin == nil){
        pin = [[[MKPinAnnotationView alloc] initWithAnnotation:annotation
                                               reuseIdentifier: @"anIdentifier"] autorelease];

        pin.pinColor = MKPinAnnotationColorRed;
        pin.animatesDrop = YES;
        pin.canShowCallout = YES;
    }
    else{
        pin.annotation = annotation;
    }
    return pin;
    }

ParkAnnotation.h

#import <Foundation/Foundation.h>
#import <MapKit/MapKit.h>

@interface ParkAnnotation : NSObject <MKAnnotation> {

    NSString *title;
    CLLocationCoordinate2D coordinate;

}


@property (nonatomic, copy) NSString *title;  
@property (nonatomic, readonly) CLLocationCoordinate2D coordinate;

- (id)initWithTitle:(NSString *)ttl andCoordinate:(CLLocationCoordinate2D)c2d;

@end

ParkAnnotation.m (edited: see Wolfgangs comments below )

#import "ParkAnnotation.h"
@implementation ParkAnnotation
@synthesize title, coordinate;
- (id)initWithTitle:(NSString *)ttl andCoordinate:(CLLocationCoordinate2D)c2d {
    self = [super init];
    if (self) { 
        title = ttl;
        coordinate = c2d;    
    } 
    return self;
}
- (void)dealloc {
    [title release];
    [super dealloc];
}
@end

Answer 1

The initializer in ParkAnnotation.m isn't written following ObjC conventions. The self variable is never set, the designated initializer of a class should follow the following pattern:

- (id)init 
{
    self = [super init]; 
    if (self) 
    { 
        /* custom initialization here ... */ 
    } 
    return self;
} 

Since self is not set, the accessor methods used in the caller will fail; the container object (inside ParkAnnotation.m referenced with self) will be nil or some bogus value when trying to access a property inside the object from another class.