关于 presentViewController 时机

2023-12-27 15:29:15

　　类似微信、QQ这些应用如果用户没有登录，会弹出登录界面，如果 presentViewController 是写在 viewDidAppear 之前，会有警告

　　Presenting view controllers on detached view controllers is discouraged

　　Unbalanced calls to begin/end appearance transitions for

大致意思是Presenting控制器还没有完全出现就模态出一个视图，产生层级问题。

将presentViewController写在视图已经出现就行 viewDidAppear 里

　　UIStoryboard 分类

@implementation UIStoryboard (Extention)
+ (__kindofUIViewController *)wl_instantiateViewControllerWithStoryboardName:(NSString *)storyboardName
                                                                   identifier:(NSString *)identifier {
    NSAssert(storyboardName.length > 0, @"参数 storyboardName 为 nil 或空字符串.");

    UIStoryboard *storyboard = [selfstoryboardWithName:storyboardName bundle:nil];

    NSAssert(storyboard, @"文件不存在 => %@", [NSString stringWithFormat:@"%@.storyboard", storyboardName]);

    if (identifier) {
        return [storyboard instantiateViewControllerWithIdentifier:identifier];
    }

    UIViewController *initialVC = [storyboard instantiateInitialViewController];

    NSAssert(initialVC, @"%@ 未指定 initial 控制器.",
             [NSString stringWithFormat:@"%@.storyboard", storyboardName]);

    return initialVC;
}

@end
对于 (__kindofUIViewController *) 是返回值可以是 UIViewController 及其子类，毕竟有时候我们需要模态出来的视图需要包装NavigationController

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