iOS中区分照片的来源

原理就是通过枚举出每个assets group，然后取得group property，group property是个整数，对应头文件中的一些枚举值。用这个可以判断照片是从哪来的（相机胶卷、照片流、相册），进一步的可以结合persistent id来判断照片的来源是从设备上创建还是来自于我的电脑

ALAssetsLibrary *library = [[ALAssetsLibrary alloc] init];

[library enumerateGroupsWithTypes:ALAssetsGroupAll

usingBlock:^(ALAssetsGroup *group, BOOL *stop)

	{

		NSLog(@"%@", group);

		[group setAssetsFilter:[ALAssetsFilter allAssets]];

		NSLog(@"名称：%@", [group valueForProperty:ALAssetsGroupPropertyName]);

NSNumber* groupType = [group valueForProperty:ALAssetsGroupPropertyType];

		switch ([groupType unsignedIntegerValue]) {

			case ALAssetsGroupAlbum:

			{
				NSLog(@"来自我的电脑或者是在设备上创建");

				NSString* persistentID = [group valueForProperty:ALAssetsGroupPropertyPersistentID];

				if ([[persistentID substringWithRange:NSRangeFromString(@"0,8")] isEqualToString:@"00000000"])

				{
					NSLog(@"来自我的电脑");
				}

				break;
			}

			case ALAssetsGroupSavedPhotos:

				NSLog(@"相机胶卷");
				break;

			case ALAssetsGroupPhotoStream:

				NSLog(@"我的照片流");
				break;

                        default:
				break;
		}
	}
	failureBlock: ^(NSError *error)
	{
		NSLog(@"No groups");
	}];