Ios catch块中未处理异常

这是我的代码，当我在UITextFields中输入错误的值时引发异常，但在引发异常后，它不会在catch语句中处理

- (IBAction)gotocanvas:(id)sender {
    @try {

        DrawObs_Probs *mainview = [self.storyboard instantiateViewControllerWithIdentifier:@"drawCanvas"];
        mainview.length = self.length.text;
        mainview.breadth = self.breadth.text;
        mainview.camheight = self.camheight.text;
        mainview.dataPath = self.dataPath;
        if ([length.text floatValue]==0.0 || [breadth.text floatValue] == 0.0 || [camheight.text floatValue] <= 1.6) {
            NSException* myException = [NSException exceptionWithName:@"Invalid" reason:@"Invalid Input Values" userInfo:nil];
            @throw myException;
        }
        [self presentViewController:mainview animated:YES completion:nil];
    }
    @catch (NSException *exception) {
        UIAlertView *alert = [[UIAlertView alloc] initWithTitle:@"Error" message:@"Enter values in numbers" delegate:self cancelButtonTitle:@"Cancel" otherButtonTitles:@"OK", nil];
        [alert show];
    }
    @finally {

    }

}

-（iAction）gotocanvas:（id）发送方{
@试一试{
DrawObs_Probs*mainview=[self.storyboard实例化控件标识符：@“drawCanvas”]；
mainview.length=self.length.text；
mainview.width=self.width.text；
mainview.camheight=self.camheight.text；
mainview.dataPath=self.dataPath；
如果（[length.text floatValue]==0.0 | |[Width.text floatValue]==0.0 | |[camheight.text floatValue]，如Paul所说，不要使用try..catch，而是使用以下方法

- (IBAction)gotocanvas:(id)sender {
    if ([length.text floatValue] == 0.0 || [breadth.text floatValue] == 0.0 || [camheight.text floatValue] <= 1.6) {
        UIAlertView *alert = [[UIAlertView alloc] initWithTitle:@"Error" message:@"Enter values in numbers" delegate:self cancelButtonTitle:@"Cancel" otherButtonTitles:@"OK", nil];
        [alert show];
        return;
    }

    DrawObs_Probs *mainview = [self.storyboard instantiateViewControllerWithIdentifier:@"drawCanvas"];
    mainview.length = self.length.text;
    mainview.breadth = self.breadth.text;
    mainview.camheight = self.camheight.text;
    mainview.dataPath = self.dataPath;

    [self presentViewController:mainview animated:YES completion:nil];
}

-（iAction）gotocanvas:（id）发送方{
如果（[length.text floatValue]==0.0 | |[Width.text floatValue]==0.0 | |[camheight.text floatValue]try..catch在Objective C中不是一种非常常见的编程模式。在这里，您可以简单地使用if语句来显示警报。您知道怎么做吗？只需将
UIAlertView
代码放在您有
NSException..
的地方，然后将
[self-presentViewController:main view动画：是完成：否]
在else中，我和ClaushAnks做了相同的逻辑：