无法识别的选择器已发送到实例？

Question

I have seen that a few others have had this problem as well. I'm trying to follow a tutorial online that shows how to create animated pins on a MapView.

I have implemented the code as shown in the tutorial and the project builds fine except I receive this exception:

-[MKPointAnnotation iconN]: unrecognized selector sent to instance

I have a subclass of 'MKPinAnnotationView' and in the .m file I create this method:

- (void)setAnnotation:(id<MKAnnotation>)annotation {
    [super setAnnotation:annotation];

    //Place *place = [[Place alloc] init];
    Place *place = (Place *)annotation;


    //The following line is where the program sends "SIGABRT"
    icon = [UIImage imageNamed:[NSString stringWithFormat:@"pin_%d.png", [place.iconN intValue]]];
    [iconView setImage:icon];
}

Here are a few parts from my "model" which is called Place.h/.m. Here is where I create the property for 'iconN'.

@property (retain, nonatomic) NSNumber *iconN;

And here I synthesize it:

@synthesize iconN = _iconN;

Any help is greatly appreciated.

EDIT: Here is the Place.h and Place.m

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


@interface Place : NSObject <MKAnnotation> {
    CLLocationCoordinate2D coordinate;
    NSString *title;
}

@property (retain, nonatomic) NSNumber *iconN;
@property (nonatomic, copy) NSString *title;
@property (nonatomic) CLLocationCoordinate2D coordinate;

- (id)initWithLong:(CGFloat)lon Lat:(CGFloat)lat iconNumber:(NSNumber *)iconNumber;

@end

And the Place.m

#import "Place.h"

@implementation Place
@synthesize coordinate;
@synthesize iconN = _iconN;
@synthesize title;

- (id)initWithLong:(CGFloat)lon Lat:(CGFloat)lat iconNumber:(NSNumber *)iconNumber {
    self = [super init];
    if (self) {
        coordinate = CLLocationCoordinate2DMake(lat, lon);
        self.iconN = iconNumber;
    }

    return self;
}

- (NSString *)title {
    return [NSString stringWithFormat:@"Bus: %d", [self.iconN intValue]];
}

- (NSString *)subtitle {
    return [NSString stringWithFormat:@"bus[%d] from database.", [self.iconN intValue] - 1];
}


@end

Answer 1

You cannot convert a MKAnnotation to a Place just by casting it. This line is wrong.

Place *place = (Place *)annotation;

You should post your Place.h and Place.m files if you're still stuck. You need to either set the iconN property on a new Place object, or create an init method in the Place class that accepts the MKAnnotation object as a parameter and sets it own internal values accordingly.

Answer 2

您正在将消息发送到注释，但是您似乎具有注释视图的子类。

Answer 3

In the line

Place *place = (Place *)annotation;

has the variable place of annotation variable class (MKPointAnnotation), you are not able to bring the master class variable to a subclass in this way. Instead you'll have to make a constructor for Place from MKPointAnnotation and perform a check in the setAnnotation method that annotation is of MKPointAnnotation.

Answer 4

Posting as an answer what was originally just a comment:

I'm not familiar with the MapKit, but the thing that sticks out for me in this: -[MKPointAnnotation iconN]: unrecognized selector sent to instance is that the class is MKPointAnnotation. So the annotation you're receiving isn't actually a Place object, it's an MKPointAnnotation object - you can't just cast to Place. I suspect the root of your problem is where you create your annotation object in the first place.