得到了如下报错：**Application tried to present a nil modal view controller on target**。我在运行的程序是，首先判断条件是否满足，启动后修改初始化视图控制器。
- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:( NSDictionary *)launchOptions
{
if(![[NSUserDefaults standardUserDefaults] boolForKey:@"logged_in"]) {
ViewControllerOne *vc1 = [[ViewControllerOne alloc]init];
vc1=[self.storyboard instantiateViewControllerWithIdentifier: @"vc1"];
[self presentViewController:vc1 animated:YES completion:Nil];
} else {
ViewControllerTwo *vc2 = [[ViewControllerTwo alloc]init];
vc2=[self.storyboard instantiateViewControllerWithIdentifier: @"vc2"];
[self presentViewController:vc2 animated:YES completion:Nil];
}
// Override point for customization after application launch.
return YES;
}
写回答
如果是从storyboard中来创建控制器不需要先
`
ViewControllerOne *vc1 = [[ViewControllerOne alloc]init];
`
修改后的代码如下：
- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions
{
UIViewController *rootVC;
self.window = [[UIWindow alloc] initWithFrame:[[UIScreen mainScreen] bounds]];
self.window.backgroundColor = [UIColor whiteColor];
if(![[NSUserDefaults standardUserDefaults] boolForKey:@"logged_in"]) {
rootVC=[self.storyboard instantiateViewControllerWithIdentifier: @"vc1"];
} else {
rootVC=[self.storyboard instantiateViewControllerWithIdentifier: @"vc2"];
}
window.rootViewConroller=rootVC;
[self.window makeKeyAndVisible];
return YES;
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