objective-c - MKMapKit-遍历MKA注释时为EXC_BAD_ACCESS

Question

我已经被困在这个EXC_BAD_ACCESS错误2天了。我有一个reloadAnnotations方法，可以在添加新注释之前删除所有注释。在删除注释之前，此方法应检查新集合是否包含相同的位置，以便不会将其删除并重新添加。但是，一旦我尝试找出当前的注释标题，就会收到此错误Thread 1: Program received signal: "EXC_BAD_ACCESS"
当我在调试器中查看批注时，标题属性会显示“无效摘要”。这一定是由于未保留值而引起的，但是我已经尝试了所有方法并且无法弄清楚。

为什么我不能将注释标题记录到NSLog？

并且为什么我不能将每个标题和座标与其他对象进行比较？

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(编辑:请参见下面的Wolfgangs评论)

#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

ParkAnnotation.m 中的初始化程序未遵循ObjC约定编写。永远不会设置self变量，指定的类初始化器应遵循以下模式:

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

由于未设置self，因此调用方中使用的访问器方法将失败；当尝试从另一个类访问该对象内部的属性时，该容器对象(在被自己引用的 ParkAnnotation.m 内部)将为nil或某些虚假值。