Question

以下代码在对fetchAssetsWithOptions的调用上抛出NSInvalidArgumentException：

PHFetchOptions *allPhotosOptions = [[PHFetchOptions alloc] init];
allPhotosOptions.sortDescriptors =
        @[[NSSortDescriptor sortDescriptorWithKey:@"creationDate" ascending:NO]];
allPhotosOptions.predicate = 
        [NSPredicate predicateWithFormat:@"pixelHeight >=  pixelWidth * 1.95" ];
self.allPhotos = [PHAsset fetchAssetsWithOptions:allPhotosOptions];

消息是

NSInvalidArgumentException ... reason: '*** -constantValue only defined for abstract class.  
    Define -[NSFunctionExpression constantValue]!'

我在谓词格式字符串上尝试了很多变体，但是当我尝试使用乘法时总是得到这个消息。我做错了什么？

Answer 1

我不确定为什么，但是当你没有将任何格式参数传递给predicateWithFormat时：并将它与Photos一起使用就会出现这个错误;

我能够通过确保传递格式参数来解决问题。所以在你的情况下：

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使用NSPredicate与照片框架的异常：定义 - [NSFunctionExpression constantValue]！

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