UIButton 选择器正在抛出'unrecognized selector'即使选择器存在

我正在视图中以编程方式创建两个按钮。两个选择器方法都存在，但它仍然抛出"无法识别的选择器"错误。我读到一些关于检查僵尸的文章。但我激活了它（xcode 4.2），没有看到任何僵尸。这是代码。。

- (void)viewDidLoad
{
    for(int i = 0; i < [list count]; i++){  
     ... if statement checks to add text fields
    }
     UIButton *submit = [UIButton buttonWithType:UIButtonTypeRoundedRect];
     [submit addTarget:self action:@selector(submission:)
     forControlEvents:UIControlEventTouchUpInside];
     [submit setTitle:@"Submit" forState:UIControlStateNormal];
     submit.frame = CGRectMake(x+ 170.0, y, 72, 37);
    UIButton *addition = [UIButton buttonWithType:UIButtonTypeRoundedRect];
    [addition addTarget:self action:@selector(addition:)
    forControlEvents:UIControlEventTouchUpInside];
    [addition setTitle:@"Additional Mission" forState:UIControlStateNormal];
    addition.frame = CGRectMake(x, y, 140, 37);
    y = y+90;
   [inputsView addSubview:submit];
   [inputsView addSubview:addition];
   [inputsView setScrollEnabled:YES];
   [inputsView setContentSize:CGSizeMake(320, y)]; 

}
 - (void)submission{
UIAlertView *alert = [[UIAlertView alloc] initWithTitle:@"Submission Complete" message:@"Submission"
                                               delegate:self cancelButtonTitle:@"No" otherButtonTitles:@"Yes", nil];
[alert show];
}
 -(void)addition{
UIAlertView *alert = [[UIAlertView alloc] initWithTitle:@"Creating Additional Mission" message:@"Additional Mission"
                                               delegate:self cancelButtonTitle:@"No" otherButtonTitles:@"Yes", nil];
[alert show];
}

有一点需要注意。。inputsView是我的视图控制器中的一个UIScrollView。

提前谢谢。