在一个控制器里面创建了
UINavigationController * nav = [[UINavigationController alloc]initWithRootViewController:self];
UIWindow * showWindow = [[UIWindow alloc] initWithFrame:[UIScreen mainScreen].bounds];
showWindow.rootViewController = nav;
[showWindow makeKeyAndVisible];
在当前控制器创建了一个 UITextField * pwdTextField;
[_pwdTextField resignFirstResponder];
为什么在放弃第一响应时总是报错呢?
NSScanner: nil string argument