判断当前授权状态，抓取自定义相册等

#pragma mark - 点击
- (IBAction)save
{
    PHAuthorizationStatus oldStatus = [PHPhotoLibrary authorizationStatus];
    
    // 判断当前的授权状态
    [PHPhotoLibrary requestAuthorization:^(PHAuthorizationStatus status) {
        switch (status) {
                // 这是系统级别的限制（比如家长控制），用户也无法修改这个授权状态
            case PHAuthorizationStatusRestricted: {
                [SVProgressHUD showErrorWithStatus:@"由于系统原因，无法保存图片！"];
                break;
            }
                
                // 用户已经拒绝当前App访问相片数据（说明用户当初选择了“Don't Allow”）
            case PHAuthorizationStatusDenied: {
                if (oldStatus != PHAuthorizationStatusNotDetermined) {
                    XMGLog(@"提醒用户去打开访问开关")
                }
                break;
            }
                
                // 用户已经允许当前App访问相片数据（说明用户当初选择了“OK”）
            case PHAuthorizationStatusAuthorized: {
                [self saveImage];
                break;
            }
                
            default:
                break;
        }
    }];
}

/**
 *  获得当前App对应的【自定义相册】
 */
- (PHAssetCollection *)createdCollection
{
    // 抓取所有【自定义相册】
    PHFetchResult<PHAssetCollection *> *collections = [PHAssetCollection fetchAssetCollectionsWithType:PHAssetCollectionTypeAlbum subtype:PHAssetCollectionSubtypeAlbumRegular options:nil];
    // 从Info.plist中获得App名称(也就是当前App的相册名称)
    NSString *title = [NSBundle mainBundle].infoDictionary[(NSString *)kCFBundleNameKey];
    for (PHAssetCollection *collection in collections) {
        if ([collection.localizedTitle isEqualToString:title]) {
            // 【自定义相册】已经创建过
            return collection;
        }
    }
    
    __block NSString *collectionId = nil;
    [[PHPhotoLibrary sharedPhotoLibrary] performChangesAndWait:^{
        // 创建【自定义相册】
        collectionId = [PHAssetCollectionChangeRequest creationRequestForAssetCollectionWithTitle:title].placeholderForCreatedAssetCollection.localIdentifier;
    } error:nil];
        
    // 根据id获得刚刚创建完的相册
    return [PHAssetCollection fetchAssetCollectionsWithLocalIdentifiers:@[collectionId] options:nil].firstObject;
}

/**
 *  保存图片
 */
- (void)saveImage
{
    // 凡是遵守NSFastEnumeration协议的对象，都可以使用for-in来遍历, for-in的效率普通for循环高
    // performChanges里面不能嵌套performChanges
    
    // 获得【自定义相册】
    PHAssetCollection *createdCollection = self.createdCollection;
    
    [[PHPhotoLibrary sharedPhotoLibrary] performChanges:^{
        // 保存图片到【相机胶卷】
        // createdAsset 就代表 刚才添加到【相机胶卷】中的图片
        PHObjectPlaceholder *createdAsset = [PHAssetChangeRequest creationRequestForAssetFromImage:self.imageView.image].placeholderForCreatedAsset;
        
        // 将对应的相册传入，创建一个【相册修改请求】对象
        PHAssetCollectionChangeRequest *collectionChangeRequest = [PHAssetCollectionChangeRequest changeRequestForAssetCollection:createdCollection];
        
        // 将保存到【相机胶卷】的图片添加到【自定义相册】
        [collectionChangeRequest insertAssets:@[createdAsset] atIndexes:[NSIndexSet indexSetWithIndex:0]];
    } completionHandler:^(BOOL success, NSError *error) {
        if (success) {
            [SVProgressHUD showSuccessWithStatus:@"保存成功！"];
        } else {
            [SVProgressHUD showErrorWithStatus:@"保存失败！"];
        }
    }];
    
//    __block NSString *assetId = nil;
//    // 凡是遵守NSFastEnumeration协议的对象，都可以使用for-in来遍历, for-in的效率普通for循环高
//    [[PHPhotoLibrary sharedPhotoLibrary] performChanges:^{
//        // 保存图片到【相机胶卷】
//        // createdAsset 就代表 刚才添加到【相机胶卷】中的图片
//        assetId = [PHAssetChangeRequest creationRequestForAssetFromImage:self.imageView.image].placeholderForCreatedAsset.localIdentifier;
//    } completionHandler:^(BOOL success, NSError *error) {
//        PHAsset *createdAsset = [PHAsset fetchAssetsWithLocalIdentifiers:@[assetId] options:nil].firstObject;
//        
//        // 将对应的相册传入，创建一个【相册修改请求】对象
//        PHAssetCollectionChangeRequest *collectionChangeRequest = [PHAssetCollectionChangeRequest changeRequestForAssetCollection:createdCollection];
//
//        // 将保存到【相机胶卷】的图片添加到【自定义相册】
//        [collectionChangeRequest insertAssets:@[createdAsset] atIndexes:[NSIndexSet indexSetWithIndex:0]];
//    }];
}

- (IBAction)back
{
    [self dismissViewControllerAnimated:YES completion:nil];
}