打破照片ALAssetsLibrary的迭代

Question

如何使用布爾集突破ALAssetsLibrary enumerateAssets方法的枚舉。 我可以擺脫循環嗎？

碼：

[self.library enumerateGroupsWithTypes:ALAssetsGroupSavedPhotos usingBlock:^(ALAssetsGroup *group, BOOL *stop) {
    @try {
        if(group != nil) {
            @autoreleasepool {
                    int newNumberOfPhotos = [group numberOfAssets];
                    if (self.numberOfPhotosInSavedPhotos < newNumberOfPhotos) {
                        //only new photos

                        NSRange range = NSMakeRange(self.numberOfPhotosInSavedPhotos, newNumberOfPhotos-self.numberOfPhotosInSavedPhotos);
                        NSIndexSet *indexSet = [NSIndexSet indexSetWithIndexesInRange:range];
                        [group enumerateAssetsAtIndexes:indexSet options:0 usingBlock:^(ALAsset *result, NSUInteger index, BOOL *stop) {
                            @autoreleasepool {
                               if(someCondition)  {
 //get out of the enumeration block (that is, exit the method) or go to complete block
                                }

                                NSString *assetType = [result valueForProperty:ALAssetPropertyType];
                            }
                        } ];
               }         
            }
        } else {
            //enumeration ended

        }

    }
    @catch (NSException *e) {
        NSLog(@"exception streaming: %@", [e description]);
    }
}failureBlock:^(NSError *error){
    NSLog(@"Error retrieving albums stream: %@", [error description]);
    if (error.code==-3312  || error.code==-3311) {
    }
}];

Answer 1

要停止資產枚舉，只需在枚舉塊中設置*stop = YES 。

如果要同時停止外部枚舉和內部枚舉，請對stop變量使用不同的名稱，並將兩者都設置為YES ：

[self.library enumerateGroupsWithTypes:ALAssetsGroupSavedPhotos usingBlock:^(ALAssetsGroup *group, BOOL *outerStop) {
    ...
    [group enumerateAssetsAtIndexes:indexSet options:0 usingBlock:^(ALAsset *result, NSUInteger index, BOOL *innerStop) {
         if (someCondition) {
             *innerStop = YES;
             *outerStop = YES;
         } else {
             // process asset
         }
     }
 }

備注：如果循環中沒有編程錯誤，通常不需要@try/@catch塊。

您對“新照片”的檢查看起來很可疑，因為每組中的資產數量與相同的數字self.numberOfPhotosInSavedPhotos ，也許您應該再次檢查該部分。