问设置UICollectionViewController - nib但没有得到UICollectionView时出错

EN

 #import <UIKit/UIKit.h>

 @interface KidsDetailViewController : UICollectionViewController <UICollectionViewDataSource>
 @property NSNumber *idCampana;

@property (weak, nonatomic) IBOutlet UICollectionView *grid;

@end

- (NSInteger)collectionView:(UICollectionView *)collectionView numberOfItemsInSection:(NSInteger)section {

  return [grid_kid count];
}


- (UICollectionViewCell *)collectionView:(UICollectionView *)collectionView cellForItemAtIndexPath:(NSIndexPath *)indexPath {

GridCell *cell = [collectionView dequeueReusableCellWithReuseIdentifier:@"MY_CELL" forIndexPath:indexPath];
cell.imageView.image = [UIImage imageNamed:self.truckImages[0]];

cell.prd_img.image = [UIImage imageNamed:@"ic_launcher_58x58"];

return cell;
}

#import <UIKit/UIKit.h>

 @interface GridCell : UICollectionViewCell
 @property (weak, nonatomic) IBOutlet UIImageView *prd_img;

@end

 #import "GridCell.h"

 @implementation GridCell

 - (instancetype)initWithFrame:(CGRect)frameRect {
      self = [super initWithFrame:frameRect];
      if (self) {
          // Initialization code
      }
   return self;
 }

 @end

   *** Assertion failure in -[KidsDetailViewController loadView], /SourceCache/UIKit_Sim/UIKit-3283.1/UICollectionViewController.m:166
   2014-07-28 02:25:18.874 Geelbe[7673:231598] *** Terminating app due to uncaught exception 'NSInternalInconsistencyException', reason: '-[UICollectionViewController loadView] loaded the "jXd-Ir-mr4-view-0IK-5Q-NzC" nib but didn't get a UICollectionView.'
  *** First throw call stack: