UIImage转PHAsset

网上很多PHAsset转UIImage的代码，没有UIImage转PHAsset的，今天有个同学刚好问，我正好研究一下，直接上代码吧：

    UIImage*image = [UIImageimageNamed:@"image"];

    [[PHPhotoLibrary sharedPhotoLibrary] performChangesAndWait:^{

        PHAssetChangeRequest *request = [PHAssetChangeRequest creationRequestForAssetFromImage:image];

        NSString *localIndentifier = request.placeholderForCreatedAsset.localIdentifier;

        PHFetchResult*assetResult = [PHAssetfetchAssetsWithLocalIdentifiers:@[localIndentifier]options:nil];

        PHAsset*asset = assetResult.firstObject;

    }error:nil];

另外需要注意，转换代码一定要写在PHPhotoLibrary的

- (void)performChanges:(dispatch_block_t)changeBlock completionHandler:(nullable void(^)(BOOL success, NSError *__nullable error))completionHandler;

或者

- (BOOL)performChangesAndWait:(dispatch_block_t)changeBlock error:(NSError *__autoreleasing *)error;

中，不然会报异常：

Terminating app due to uncaught exception 'NSInternalInconsistencyException', reason: 'This method can only be called from inside of -[PHPhotoLibrary performChanges:completionHandler:] or -[PHPhotoLibrary performChangesAndWait:error:]'