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I have a single view controller acting as both the dataSource and delegate for a UICollectionView. 

- (UICollectionViewCell *)collectionView:(UICollectionView *)cv cellForItemAtIndexPath:(NSIndexPath *)indexPath {
    PhotoCell *cell = [cv dequeueReusableCellWithReuseIdentifier:@"PIC_CELL" forIndexPath:indexPath];
    UIImage *photo = [UIImage imageWithData:[[_fetchedImages objectAtIndex:indexPath.row] valueForKey:@"picture"]];
    if (photo) {
        cell.photo = photo;
    }
    return cell;
}

In the above method I instantiate a custom collection view cell and attempt to set the photo property of it.

PhotoCell.h

@interface PhotoCell : UICollectionViewCell {
}

@property (nonatomic, strong) IBOutlet UIImageView *imageView;
@property (nonatomic, strong) UIImage *photo;

@end

PhotoCell.m

@implementation PhotoCell

- (id)initWithCoder:(NSCoder *)aDecoder {
    self = [super initWithCoder:aDecoder];
    if (self) {
        //customization
    }
    return self;
}

- (void)setPhoto:(UIImage *)photo {
    UIGraphicsBeginImageContextWithOptions(CGSizeMake(83.0, 83.0), NO, 0.0);
    [photo drawInRect:CGRectMake(0, 0, 83, 83)];
    UIImage *newImage = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();
    if (_photo != newImage)
        _photo = newImage;

    self.imageView.image = _photo;
}

Here, I override the photo property's setter, allowing for resizing of the passed photo before setting it as the property.

However, when the code executes and a PhotoCell custom cell is instantiated, the following error is thrown when attempting to set the photo property in the -cellForItemAtIndexPath: method:

    -[UICollectionViewCell setPhoto:]: unrecognized selector sent to instance 0x155c1270
*** Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '-[UICollectionViewCell setPhoto:]: unrecognized selector sent to instance 0x155c1270'

It seems that the system is perceiving the custom cell as an instance of its superclass, UICollectionViewCell, rather than the actual class, PhotoCell. The same error is thrown when not overriding the setter.

Why is the customized cell being seen as an instance of its superclass, causing the setter to be unrecognizable?

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1 回答 1

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问题与您的注册方式有关PIC_CELL。无论在哪里完成，都指定了错误的类。这可能在 XIB 文件或您的代码中。

于 2013-06-12T22:51:27.733 回答