//访问保存照片
UIImageWriteToSavedPhotosAlbum(UIImage *image,id completionTarget,SEL completionSelector,void *contextInfo);

//只能调用这个方法
- (void)image:(UIImage *)image didFinishSavingWithError:(NSError *)error contextInfo:(void *)contextInfo;


//Swfit2.0中要改变这个方法 - (void)image:(UIImage *)image didFinishSavingWithError:(NSError *) error contextInfo: (void *) contextInfo;

改变方法为：

//解释：didFinishSavingWithError为外部参数。 在OC中有两个contextInfo ，Swift中自动推断后，删除一个contextInfo.

@objc private func image(image: UIImage,didFinishSavingWithError error:NSError?,contextInfo: AnyObject) {

print("保存成功")
}

调用：

UIImageWriteToSavedPhotosAlbum(image,self,"image:didFinishSavingWithError:contextInfo:",nil)