在XIB中加载MKMapView会引发符合关键值编码的＆＃39;错误

Question

目标：尝试在我的ViewController中重用UIView用于不同的xib文件。一个xib有一个MKMapView IBOutlet，另一个xib有一个cameraView（不包含在下面的代码中）。

问题：在没有任何IBOutlets的情况下交换XIB文件工作正常但是当我在其中一个xib文件中添加了一个用于MKMapView的IBOutlet时，它会抛出此错误：

＆＃34;原因：＆＃39; [setValue：forUndefinedKey：]：此类与键映射不符合键值编码＆＃34;

xib文件：

MapView.h

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

@interface MapView : UIView <MKMapViewDelegate>
@property (weak, nonatomic) IBOutlet MKMapView *map;
@end

MapView.m

#import "MapView.h"
#import <MapKit/MapKit.h>

@implementation MapView 

-(id) initWithCoder:(NSCoder *)aDecoder
{
     if (self = [super initWithCoder:aDecoder])
{

    [self load];
 }
return self;
}

-(id)initWithFrame:(CGRect)frame
{
    if (self = [super initWithFrame:frame])
    {
      [self load];
 }
return self;
}

-(void)load
{
    UIView *view = [[[NSBundle bundleForClass:[self class]]       loadNibNamed:@"MapView" owner:self options:nil] firstObject];
    [self addSubview:view];
    view.frame = self.bounds;
}

@end

的ViewController：

DashboardViewController：

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

@interface DasboardViewController : UIViewController <MKMapViewDelegate>

@end

DashboardViewController.m：

#import "DasboardViewController.h"
#import "MapView.h"
@interface DasboardViewController ()
@property (strong, nonatomic) IBOutlet UIView *viewMain;
@property(nonatomic, strong) MapView *mapNib;
@end

@implementation DasboardViewController

- (void)viewDidLoad {
    [super viewDidLoad];

    _mapNib = [[NSBundle mainBundle] loadNibNamed:@"MapView"   owner:self options:nil].firstObject;
    [_mapNib setFrame:_viewMain.bounds];
    [_mapNib setAutoresizingMask:UIViewAutoresizingFlexibleWidth |   UIViewAutoresizingFlexibleHeight];
    [_viewMain addSubview:_mapNib];

}

- (void)didReceiveMemoryWarning {
    [super didReceiveMemoryWarning];
    // Dispose of any resources that can be recreated.
}

@end