//资源库更新
extern NSString *const ALAssetLibraryUpdatedAssetsKey;
//插入组
extern NSString *const ALAssetLibraryInsertedAssetGroupsKey;
//更新组
extern NSString *const ALAssetLibraryUpdatedAssetGroupsKey;
//删除组
extern NSString *const ALAssetLibraryDeletedAssetGroupsKey;
下面列举了操作过程中的一些异常定义：
enum {
ALAssetsLibraryUnknownError = -1, // 未知错误
ALAssetsLibraryWriteFailedError = -3300, //写入错误
ALAssetsLibraryWriteBusyError = -3301, // 写入繁忙 可以重试
ALAssetsLibraryWriteInvalidDataError = -3302, // 无效数据
ALAssetsLibraryWriteIncompatibleDataError = -3303, // 不兼容的数据
ALAssetsLibraryWriteDataEncodingError = -3304, // 数据编码错误
ALAssetsLibraryWriteDiskSpaceError = -3305, // 内存不足
ALAssetsLibraryDataUnavailableError = -3310, // 数据不可用
ALAssetsLibraryAccessUserDeniedError = -3311, // 权限错误
ALAssetsLibraryAccessGloballyDeniedError = -3312, // 权限错误
};
四、ALAssetsGroup资源组对象
资源组其实就是对应与我们相册中的一组资源，我们可以通过如下的方便遍历出其中的所有资源：
_library = [[ALAssetsLibrary alloc]init];
[_library enumerateGroupsWithTypes:ALAssetsGroupAll usingBlock:^(ALAssetsGroup *group, BOOL *stop) {
if (group) { // 遍历相册还未结束
// 设置过滤器
[group setAssetsFilter:[ALAssetsFilter allPhotos]];
if (group.numberOfAssets) {
[group enumerateAssetsUsingBlock:^(ALAsset *result, NSUInteger index, BOOL *stop) {
NSLog(@"%d:%@",index,result);
}];
}
} else { // 遍历结束（当group为空的时候就意味着结束）
NSLog(@"没有相册列表了");
}
} failureBlock:^(NSError *error) {
NSLog(@"失败");
}];
ALAssetsGroup中相关方法解析如下：
//获取相关属性
/*
extern NSString *const ALAssetsGroupPropertyName;//组名字
extern NSString *const ALAssetsGroupPropertyType;//组类型
extern NSString *const ALAssetsGroupPropertyPersistentID; //ID
extern NSString *const ALAssetsGroupPropertyURL;//组URL
*/
- (id)valueForProperty:(NSString *)property;
//获取当前组的缩略图海报
- (CGImageRef)posterImage;
//设置过滤器
- (void)setAssetsFilter:(ALAssetsFilter *)filter;
//获取组中资源个数
- (NSInteger)numberOfAssets;
//进行资源枚举
- (void)enumerateAssetsUsingBlock:(ALAssetsGroupEnumerationResultsBlock)enumerationBlock;
/*
typedef NS_OPTIONS(NSUInteger, NSEnumerationOptions) {
NSEnumerationConcurrent = (1UL << 0),//顺序枚举
NSEnumerationReverse = (1UL << 1), //逆序枚举
};
*/
- (void)enumerateAssetsWithOptions:(NSEnumerationOptions)options usingBlock:(ALAssetsGroupEnumerationResultsBlock)enumerationBlock;
- (void)enumerateAssetsAtIndexes:(NSIndexSet *)indexSet options:(NSEnumerationOptions)options usingBlock:(ALAssetsGroupEnumerationResultsBlock)enumerationBlock;
//获取当前组是否允许编辑
@property (nonatomic, readonly, getter=isEditable) BOOL editable;
//向组中添加一个资源
- (BOOL)addAsset:(ALAsset *)asset;
