使用未声明的标识符“警报”

Question

I am getting an error that says: Use of undeclared identifier 'alert'

NSAlert *alert = [NSAlert alertWithMessageText: @"Why ? "
                                         defaultButton:@"OK"
                                       ];

Can someone tell me why am i getting this error ?

Updated:

Answer 1

I think you mean

UIAlertView *alert

Not

NSAlert *alert // "NSAlert" does not exist in the Cocoa API.

Your clue from the compiler is that it says the type NSAlert is undefined. If the type is undefined, then you can get another error about the variable itself being undefined, which is why it says alert is undefined.

Answer 2

For OS 8 & above use UIAlertController & for below use UIAlertview.

if(SYSTEM_VERSION_LESS_THAN(@"8.0"))
{
    alertView = [[UIAlertView alloc] initWithTitle:@"Warning" message:@"Please enter CVV2 code." delegate:self cancelButtonTitle:@"OK" otherButtonTitles:nil];
    [alertView show];
    txt_CVV2CodeResult.text = @"";
}
else
{
    UIAlertController *alertController = [UIAlertController alertControllerWithTitle:@"Warning:" message:@"Please enter CVV2 code." preferredStyle:UIAlertControllerStyleAlert];
    UIAlertAction *OKAction = [UIAlertAction
                               actionWithTitle:NSLocalizedString(@"OK", @"OK action")
                                         style:UIAlertActionStyleDefault
                                       handler:^(UIAlertAction *action)
                                       {

                                       }];

    [alertController addAction:OKAction];

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

Answer 3

For iOS, you need UIAlertView, not NSAlert. NSAlert is a Mac OS X class.

Refer

Where is NSAlert.h in the iOS SDK?