ios - 通过if-else条件的iOS表单验证错误无法正常工作

Question

我编写了一个简单的应用程序，用于验证用户输入(是否为NULL或长于定义的长度)。当验证失败时，它应该返回验证错误消息，否则，将重定向到另一个页面。

但是，该应用程序仅返回所有情况的第一个条件(用户名为空)的消息。 (例如，用户名已填写，密码为空，等等。)

m文件:

- (IBAction)doLogin {

 if(uname.text==NULL) {
     UIAlertView *err1 = [[UIAlertView alloc]
                                     initWithTitle:@"Required field!" message:@"Username is empty." delegate:nil cancelButtonTitle:@"OK" otherButtonTitles:nil];
     [err1 show];
 NSLog(@"%@",uname.text);         
 }

 else if(passw.text==NULL) {
     UIAlertView *err2 = [[UIAlertView alloc]
                               initWithTitle:@"Required field!" message:@"Password is empty." delegate:nil cancelButtonTitle:@"OK" otherButtonTitles:nil];
     [err2 show];
 NSLog(@"%@",passw.text);
 }

 else if (uname.text.length < 6)
 {
     UIAlertView *err3 = [[UIAlertView alloc]
                               initWithTitle:@"Invalid!" message:@"Enter a username longer than 6 chars." delegate:nil cancelButtonTitle:@"OK" otherButtonTitles:nil];
     [err3 show];
 NSLog(@"%@",uname.text);
 }

 else if (uname.text.length < 8)
 {
     UIAlertView *err4 = [[UIAlertView alloc]
                               initWithTitle:@"Invalid!" message:@"Enter a password longer than 8 chars." delegate:nil cancelButtonTitle:@"OK" otherButtonTitles:nil];
     [err4 show];
 NSLog(@"%@",uname.text);
 }
 else {
     /*UIAlertView *alert = [[UIAlertView alloc] initWithTitle:@"" message:@"Thank you" delegate:self cancelButtonTitle:@"Close" otherButtonTitles:@"OK", nil];
     [alert show];*/
UIViewController* flipViewController = [[UIViewController alloc] initWithNibName:@"flip" bundle:[NSBundle mainBundle]];
[self.view addSubview:flipViewController.view];

}

Answer 1

-(BOOL)isFormDataValid{

    NSString *errorMessage = nil;
    UITextField *errorField;

    if([nameTextField.text isEqualToString:@""])
    {
        errorMessage = @"Please enter username";
        errorField = nameTextField;
    }
    else if([[nameTextField.text stringByTrimmingCharactersInSet:[NSCharacterSet whitespaceCharacterSet]] length]==0)
    {
        errorMessage = @"white spaces not allowed";
        errorField = nameTextField;
    }
    else if([passwordTextField.text isEqualToString:@""])
    {
        errorMessage = @"Please enter password";
        errorField = passwordTextField;
    }
    else if([[passwordTextField.text stringByTrimmingCharactersInSet:[NSCharacterSet whitespaceCharacterSet]] length]==0)
    {
        errorMessage = @"white spaces not allowed";
        errorField = passwordTextField;
    }
if (errorMessage) {
        UIAlertView *alert = [[UIAlertView alloc] initWithTitle:@"Failed!" message:errorMessage delegate:nil cancelButtonTitle:@"OK" otherButtonTitles:nil];
        [alert show];
        [alert release];
        [errorField becomeFirstResponder];
        return NO;
    }else{
        return YES;
    }

}