ios - 错误:无效方法'undo:'不应该返回值

Question

我在以下代码行中收到此错误(无效方法'undo:'不应返回value):

return image;

有什么问题，有人知道该错误的解决方案吗？

代码:

- (IBAction)undo:(id)sender
{
NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory,
                                                     NSUserDomainMask, YES);
NSString *documentsDirectory = [paths objectAtIndex:0];
NSString* path = [documentsDirectory stringByAppendingPathComponent:
                  @"test.png" ];
UIImage* image = [UIImage imageWithContentsOfFile:path];
[self->_imagView setImage:image];
return image;
}

编辑:

如果点击了“撤消”按钮，我该怎么说呢？

码:

- (IBAction)undo:(id)sender

{

}

- (UIImage*)loadImage
{
NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory,
                                                     NSUserDomainMask, YES);
NSString *documentsDirectory = [paths objectAtIndex:0];
NSString* path = [documentsDirectory stringByAppendingPathComponent:
                  @"test.png" ];
UIImage* image = [UIImage imageWithContentsOfFile:path];
return image;
}

- (void)saveImage: (UIImage*)image
{
   if (image != nil)
   {
      NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory,
                                                         NSUserDomainMask, YES);
      NSString *documentsDirectory = [paths objectAtIndex:0];
      NSString* path = [documentsDirectory stringByAppendingPathComponent:
                      @"test.png" ];
      NSData* data = UIImagePNGRepresentation(image);
      [data writeToFile:path atomically:YES];
   }
}

Answer 1

您不能从具有void返回类型的方法中返回值。 IBAction实际上只是void。

除了尝试返回它之外，您还需要对image进行其他操作。