使用UIImageWriteToSavedPhotosAlbum直接保存

//OC

- (void)saveButtonEventWithImage:(UIImage *)image
{
    //保存完后调用的方法
    SEL selector = @selector(onCompleteCapture:didFinishSavingWithError:contextInfo:);
    //保存
    UIImageWriteToSavedPhotosAlbum(image, self, selector, NULL);
}

//图片保存完后调用的方法
- (void)onCompleteCapture:(UIImage *)screenImage didFinishSavingWithError:(NSError *)error contextInfo:(void *)contextInfo
{
    if (error){
        //保存失败
    }else {
        //保存成功
    }
}

//swift

func saveButtonEventWithImage(image: UIImage) {
    //保存完后调用的方法
     let selector = #selector(ViewController.onCompleteCapture(image:error:contextInfo:))
    //保存
     UIImageWriteToSavedPhotosAlbum(image, self, selector, nil)
}

//图片保存完后调用的方法
func onCompleteCapture(image: UIImage, error: NSError?, contextInfo: UnsafeRawPointer) {
     if error == nil {
        //保存失败
    }else {
        //保存成功
    }
}

优点：简单，方便

使用Photos框架提供的方法

//oc

- (void)getPhotoUrlSaveButtonEventWithImage:(UIImage *)image success: (void(^)(NSURL *photoUrl))completionHandler {
    __weak typeof(self) weakSelf = self;
    [[PHPhotoLibrary sharedPhotoLibrary] performChanges:^{

        PHAssetChangeRequest *result = [PHAssetChangeRequest creationRequestForAssetFromImage:image];
        PHObjectPlaceholder *assetPlaceholder = result.placeholderForCreatedAsset;
        //imageLocalIdentifier用于零时存取相片的标识符，方便后边能够取出此相片
        weakSelf.imageLocalIdentifier = assetPlaceholder.localIdentifier;
    } completionHandler:^(BOOL success, NSError * _Nullable error) {

        if (success) {
            //保存成功后通过前边的identifier得到其路径
            PHFetchResult<PHAsset *> *assets = [PHAsset fetchAssetsWithLocalIdentifiers:@[weakSelf.imageLocalIdentifier] options:nil];
            PHAsset *asset = assets[0];
            [asset requestContentEditingInputWithOptions:nil completionHandler:^(PHContentEditingInput * _Nullable contentEditingInput, NSDictionary * _Nonnull info) {
                completionHandler(contentEditingInput.fullSizeImageURL);
            }];
        }
    }];
}

//swift

func getPhotoUrlSaveButtonEventWithImage(image: UIImage, completionHandler: @escaping ((URL) -> Void)) {
        PHPhotoLibrary.shared().performChanges({ [weak self]() -> Void in
            
            let result = PHAssetChangeRequest.creationRequestForAsset(from: image)
            let assetPlaceholder = result.placeholderForCreatedAsset
            if let identifier = assetPlaceholder?.localIdentifier {
                //imageLocalIdentifier用于零时存取相片的标识符，方便后边能够取出此相片
                self?.imageLocalIdentifier = identifier
            }
        }) { [weak self](success: Bool, error: Error?) in
            
            if success {
                //保存成功后通过前边的identifier得到其路径
                let assets = PHAsset.fetchAssets(withLocalIdentifiers: [self!.imageLocalIdentifier], options: nil)
                let asset = assets.firstObject
                asset?.requestContentEditingInput(with: nil, completionHandler: { (contentEditingInput: PHContentEditingInput?, info: [AnyHashable : Any]) in
                    
                    if let url = contentEditingInput?.fullSizeImageURL {
                        completionHandler(url)
                    }
                })
            }
        }
    }

注意：此方法需导入Photos库，并且#import <Photos/Photos.h>

优点：可以直接获取到保存后的路径，方便使用