ShopCollectionViewLayout.h' file not found

老师，不知道为什么报错，这是ShopCollectionViewLayout.m

#import "ShopCollectionViewLayout.h"

#import "Util.h"

@interface ShopCollectionViewLayout(){

     NSMutableArray *attsArray;

}

@end

@implementation ShopCollectionViewLayout

-(void)prepareLayout{

    [super prepareLayout];

    if (attsArray ==nil){

        attsArray =[[NSMutableArray alloc]init];

    }

    NSInteger count = [self.collectionView numberOfItemsInSection:0];

    for (int i =0;i<count ;i++){

        NSIndexPath *indexPath =[NSIndexPath indexPathForItem:i inSection:0];

        UICollectionViewLayoutAttributes *att = [self layoutAttributesForItemAtIndexPath:indexPath];

        [attsArray addObject:att];

    }

}

-(CGSize)collectionViewContentSize{

    return CGSizeMake(SCREEN_WIDTH, SCREEN_HEIGHT);

}

-(NSArray<UICollectionViewLayoutAttributes *> *)layoutAttributesForElementsInRect:(CGRect)rect{

    return attsArray;

}

-(UICollectionViewLayoutAttributes *)

layoutAttributesForItemAtIndexPath:(NSIndexPath *)indexPath{

    UICollectionViewLayoutAttributes *att =[UICollectionViewLayoutAttributes layoutAttributesForCellWithIndexPath:indexPath];

    CGFloat w =((SCREEN_WIDTH-32)/3);

    CGFloat h = ((SCREEN_WIDTH-32)/3);

    CGFloat x =8+(indexPath.row%3)*(w+8);

    CGFloat y =8;

    if (indexPath.row>=3){

        y=16+h;

    }

    if (indexPath.row>=6){

        y=24+h*2;

    }

    if (indexPath.row>=9){

        y=32+h*3;

    }

    att.frame = CGRectMake(x, y, w, h);

    return att;

}

@end

这是ShopCollectionViewLayout.h

#import <UIKit/UIKit.h>

@interface ShopCollectionViewLayout : UICollectionViewLayout

@end

这是"MsdViewController.m"在这里报的错 ShopCollectionViewLayout.h' file not found

#import "MsdViewController.h"

#import "Util.h"

#import "ShopCollectionViewLayout.h"

#import "ShopCollectionViewCell.h"

@interface MsdViewController ()<UICollectionViewDelegate,UICollectionViewDataSource>{

    }

@property (nonatomic,copy)NSMutableArray *dataSourceArray;

@end

@implementation MsdViewController