- (IBAction)save
{
    PHAuthorizationStatus oldStatus = [PHPhotoLibrary authorizationStatus];
    
    // 判斷當(dāng)前的授權(quán)狀態(tài)
    [PHPhotoLibrary requestAuthorization:^(PHAuthorizationStatus status) {
//        [[NSOperationQueue mainQueue] addOperationWithBlock:^{
//            switch (status) {
//                    // 這是系統(tǒng)級(jí)別的限制（比如家長控制），用戶也無法修改這個(gè)授權(quán)狀態(tài)
//                case PHAuthorizationStatusRestricted: {
//                    [SVProgressHUD showErrorWithStatus:@"由于系統(tǒng)原因，無法保存圖片！"];
//                    break;
//                }
//                    
//                    // 用戶已經(jīng)拒絕當(dāng)前App訪問相片數(shù)據(jù)（說明用戶當(dāng)初選擇了“Don't Allow”）
//                case PHAuthorizationStatusDenied: {
//                    if (oldStatus != PHAuthorizationStatusNotDetermined) {
//                        XMGLog(@"提醒用戶去打開訪問開關(guān)")
//                    }
//                    break;
//                }
//                    
//                    // 用戶已經(jīng)允許當(dāng)前App訪問相片數(shù)據(jù)（說明用戶當(dāng)初選擇了“OK”）
//                case PHAuthorizationStatusAuthorized: {
//                    [self saveImage];
//                    break;
//                }
//                    
//                default:
//                    break;
//            }
//        }];
        
        dispatch_async(dispatch_get_main_queue(), ^{
            switch (status) {
                    // 這是系統(tǒng)級(jí)別的限制（比如家長控制），用戶也無法修改這個(gè)授權(quán)狀態(tài)
                case PHAuthorizationStatusRestricted: {
                    [SVProgressHUD showErrorWithStatus:@"由于系統(tǒng)原因，無法保存圖片！"];
                    break;
                }
                    
                    // 用戶已經(jīng)拒絕當(dāng)前App訪問相片數(shù)據(jù)（說明用戶當(dāng)初選擇了“Don't Allow”）
                case PHAuthorizationStatusDenied: {
                    if (oldStatus != PHAuthorizationStatusNotDetermined) {
                        XMGLog(@"提醒用戶去打開訪問開關(guān)")
                    }
                    break;
                }
                    
                    // 用戶已經(jīng)允許當(dāng)前App訪問相片數(shù)據(jù)（說明用戶當(dāng)初選擇了“OK”）
                case PHAuthorizationStatusAuthorized: {
                    [self saveImage];
                    break;
                }
                    
                default:
                    break;
            }
        });
    }];
}

/**
 *  獲得當(dāng)前App對(duì)應(yīng)的【自定義相冊(cè)】
 */
- (PHAssetCollection *)createdCollection
{
    // 抓取所有【自定義相冊(cè)】
    PHFetchResult<PHAssetCollection *> *collections = [PHAssetCollection fetchAssetCollectionsWithType:PHAssetCollectionTypeAlbum subtype:PHAssetCollectionSubtypeAlbumRegular options:nil];
    // 從Info.plist中獲得App名稱(也就是當(dāng)前App的相冊(cè)名稱)
    NSString *title = [NSBundle mainBundle].infoDictionary[(NSString *)kCFBundleNameKey];
    for (PHAssetCollection *collection in collections) {
        if ([collection.localizedTitle isEqualToString:title]) {
            // 【自定義相冊(cè)】已經(jīng)創(chuàng)建過
            return collection;
        }
    }
    
    __block NSString *collectionId = nil;
    [[PHPhotoLibrary sharedPhotoLibrary] performChangesAndWait:^{
        // 創(chuàng)建【自定義相冊(cè)】
        collectionId = [PHAssetCollectionChangeRequest creationRequestForAssetCollectionWithTitle:title].placeholderForCreatedAssetCollection.localIdentifier;
    } error:nil];
        
    // 根據(jù)id獲得剛剛創(chuàng)建完的相冊(cè)
    return [PHAssetCollection fetchAssetCollectionsWithLocalIdentifiers:@[collectionId] options:nil].firstObject;
}

/**
 *  保存圖片
 */
- (void)saveImage
{
    // 凡是遵守NSFastEnumeration協(xié)議的對(duì)象，都可以使用for-in來遍歷, for-in的效率普通for循環(huán)高
    // performChanges里面不能嵌套performChanges
    
    // 獲得【自定義相冊(cè)】
    PHAssetCollection *createdCollection = self.createdCollection;
    
    [[PHPhotoLibrary sharedPhotoLibrary] performChanges:^{
        // 保存圖片到【相機(jī)膠卷】
        // createdAsset 就代表 剛才添加到【相機(jī)膠卷】中的圖片
        PHObjectPlaceholder *createdAsset = [PHAssetChangeRequest creationRequestForAssetFromImage:self.imageView.image].placeholderForCreatedAsset;
        
        // 將對(duì)應(yīng)的相冊(cè)傳入，創(chuàng)建一個(gè)【相冊(cè)修改請(qǐng)求】對(duì)象
        PHAssetCollectionChangeRequest *collectionChangeRequest = [PHAssetCollectionChangeRequest changeRequestForAssetCollection:createdCollection];
        
        // 將保存到【相機(jī)膠卷】的圖片添加到【自定義相冊(cè)】
        [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??！"];
        }
    }];
}

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