Question

When i run my app, it crashes and i got this error:

Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '-[AnnotationsDisplay coordinate]: unrecognized selector sent to instance 0x795bda0'

AnnotationsDisplay it’s a class to manage displaying the PINS on the Map.

EDIT:
This is my AnnotationsDisplay class code:

#import <Foundation/Foundation.h>
#import <MapKit/MapKit.h>
@interface AnnotationsDisplay : NSObject<MKAnnotation> {
    NSString *title;
    CLLocationCoordinate2D coordinate;
}
- (id)initWithTitle:(NSString *)ttl andCoordinate:(CLLocationCoordinate2D)c2d;
@end

.m:

#import "AnnotationsDisplay.h"

@implementation AnnotationsDisplay
- (id)initWithTitle:(NSString *)ttl andCoordinate:(CLLocationCoordinate2D)c2d {
    title = ttl;
    coordinate = c2d;
    return self;
}
@end

Answer 1

@protocol MKAnnotation <NSObject>

// Center latitude and longitude of the annotion view.
// The implementation of this property must be KVO compliant.
@property (nonatomic, readonly) CLLocationCoordinate2D coordinate;

@optional

// Title and subtitle for use by selection UI.
@property (nonatomic, readonly, copy) NSString *title;
@property (nonatomic, readonly, copy) NSString *subtitle;

// Called as a result of dragging an annotation view.
- (void)setCoordinate:(CLLocationCoordinate2D)newCoordinate NS_AVAILABLE(NA, 4_0);

@end

Properties are already declared in MKAnnotation protocol. Just add @synthesize for each property.