ios - UIAlertController 给出错误

我是 IOS 新手。我有一个示例项目并尝试在此基础上学习 Obj-C。

现在我正在学习如何使用 UIAlertController。 我有这样的代码:

if (loanAmount == 0) { 

 UIAlertController *ErrorMessage    =[UIAlertController alertControllerWithTitle"Invalid amount" message"Enter a valid number"   preferredStyle:UIAlertControllerStyleAlert]; 
   } else 
 { // sets labels
  self.interestLabel.text = [NSString  stringWithFormat"%i%c",interestRate,percentage];   
self.periodLabel.text = [NSString stringWithFormat"%i months",months]; 
self.totalLabel.text = [NSString stringWithFormat"$%i",(loanAmount + tinterest)];

================================================ ==========================

但是当我运行模拟器时。模拟器上应该有弹出消息。取而代之的是一个错误:

015-10-11 13:56:39.985 iBank[8055:1231178] Attempting to load the view of a view controller while it is deallocating is not allowed and may result in undefined behavior (<UIAlertController: 0x7ca82400>)

任何帮助将不胜感激

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Best Answer-推荐答案

试试这个

if (loanAmount == 0) { 
UIAlertController * ErrorMessage = [UIAlertController
                          alertControllerWithTitle"Invalid amount"
                          message"Enter a valid number" 
                          preferredStyle:UIAlertControllerStyleAlert];

UIAlertAction *cancelAction = [UIAlertAction 
        actionWithTitle:NSLocalizedString(@"Cancel", @"Cancel action")
                  style:UIAlertActionStyleCancel
                handler:^(UIAlertAction *action)
                {
                  NSLog(@"Cancel action");
                }];

UIAlertAction *okAction = [UIAlertAction 
        actionWithTitle:NSLocalizedString(@"OK", @"OK action")
                  style:UIAlertActionStyleDefault
                handler:^(UIAlertAction *action)
                {
                  NSLog(@"OK action");
                }];

[ErrorMessage addAction:cancelAction];
[ErrorMessage addActionkAction];
[self presentViewController: ErrorMessage animated:YES completion:nil];
 }
 else
 {
  self.interestLabel.text = [NSString  stringWithFormat"%i%c",interestRate,percentage];   
self.periodLabel.text = [NSString stringWithFormat"%i months",months]; 
self.totalLabel.text = [NSString stringWithFormat"$%i",(loanAmount + tinterest)];
  }

关于ios - UIAlertController 给出错误，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/33064696/