iOS9图片保存到相册

 [PHPhotoLibrary requestAuthorization:^( PHAuthorizationStatus status ) {

                        // To preserve the metadata, we create an asset from the JPEG NSData representation.

                        // Note that creating an asset from a UIImage discards the metadata.
                        // In iOS 9, we can use -[PHAssetCreationRequest addResourceWithType:data:options].
                        // In iOS 8, we save the image to a temporary file and use +[PHAssetChangeRequest creationRequestForAssetFromImageAtFileURL:].
                        if ( [PHAssetCreationRequest class] ) {
                            [[PHPhotoLibrary sharedPhotoLibrary] performChanges:^{
                                [[PHAssetCreationRequest creationRequestForAsset] addResourceWithType:PHAssetResourceTypePhoto data:imageData options:nil];
                            } completionHandler:^( BOOL success, NSError *error ) {
                                if ( ! success ) {
                                    NSLog( @"Error occurred while saving image to photo library: %@", error );
                                }
                            }];
                        }
                        else { // iOS8
                            NSString *temporaryFileName = [NSProcessInfo processInfo].globallyUniqueString;
                            NSString *temporaryFilePath = [NSTemporaryDirectory() stringByAppendingPathComponent:[temporaryFileName stringByAppendingPathExtension:@"jpg"]];
                            NSURL *temporaryFileURL = [NSURL fileURLWithPath:temporaryFilePath];
                           
                            [[PHPhotoLibrary sharedPhotoLibrary] performChanges:^{
                                NSError *error = nil;
                                [imageData writeToURL:temporaryFileURL options:NSDataWritingAtomic error:&error];
                                if ( error ) {
                                    NSLog( @"Error occured while writing image data to a temporary file: %@", error );
                                }
                                else {
                                    [PHAssetChangeRequest creationRequestForAssetFromImageAtFileURL:temporaryFileURL];
                                }
                            } completionHandler:^( BOOL success, NSError *error ) {
                                if ( ! success ) {
                                    NSLog( @"Error occurred while saving image to photo library: %@", error );
                                }
                               
                                // Delete the temporary file.
                                [[NSFileManager defaultManager] removeItemAtURL:temporaryFileURL error:nil];
                            }];

                        }

                    

                }];