如何使用Objective C的PHFetchOptions只获取喜爱的图片

Question

我可以通过这样做来获取某个日期范围内的照片，但是如何进一步根据它们的favorite状态进行过滤呢？

PHFetchOptions *fetchOptions = [PHFetchOptions new];
fetchOptions.predicate = [NSPredicate predicateWithFormat:@"(creationDate >= %@) && (creationDate <= %@)",startDateMinus24Hours,endDatePlus24Hours];
_assetsFetchResults = [PHAsset fetchAssetsWithOptions:fetchOptions];

我在谷歌上搜索了"PHFetchOptions predicate favorites"，但是没有找到答案。如果您知道确切的答案，或者对谓词语法的引用，请让我知道。谢谢!

Answer 1

我想通了。

PHFetchOptions *fetchOptions = [PHFetchOptions new];
NSString *format = @"(creationDate >= %@) && (creationDate <= %@)";
if (showFavoritePhotosOnly) {
    format = [format stringByAppendingString:@" && (favorite == true)"];
}
fetchOptions.predicate = [NSPredicate predicateWithFormat:format,startDateMinus24Hours,endDatePlus24Hours]; //iwashere
_assetsFetchResults = [PHAsset fetchAssetsWithOptions:fetchOptions];