不久前，苹果WWDC19开发者大会在美国加州圣何塞举行。这次大会上，苹果公布了 iOS13 的更新内容，今天我们来看看如何适配 iOS13.
第三方登录
Sign In with Apple will be available for beta testing this summer. It will be required as an option for users in apps that support third-party sign-in when it is commercially available later this year.
如果 APP 支持三方登陆（Facbook、Google、微信、QQ、支付宝等），就必须支持苹果登，且要放前边.
黑夜模式
Apps on iOS 13 are expected to support dark mode
Use system colors and materials
Create your own dynamic colors and images Leverage flexible infrastructure
审核强制要求适配黑夜模式。
KVC 限制
iOS13 以后已经不能肆无忌惮的通过 KVC 来修改一些没有暴露出来的属性了。
*** Terminating app due to uncaught exception ‘NSGenericException’, reason: ‘Access to xxx’s _xxx ivar is prohibited. This is an application bug’
已知：
// UITextField 的 _placeholderLabel
[textField setValue:[UIColor xxx] forKeyPath:@"_placeholderLabel.textColor"];
// UISearchBar 的 _searchField
[searchBar valueForKey:@"_searchField"];模态弹出默认交互改变
/*
Defines the presentation style that will be used for this view controller when it is presented modally. Set this property on the view controller to be presented, not the presenter.
If this property has been set to UIModalPresentationAutomatic, reading it will always return a concrete presentation style. By default UIViewController resolves UIModalPresentationAutomatic to UIModalPresentationPageSheet, but other system-provided view controllers may resolve UIModalPresentationAutomatic to other concrete presentation styles.
Defaults to UIModalPresentationAutomatic on iOS starting in iOS 13.0, and UIModalPresentationFullScreen on previous versions. Defaults to UIModalPresentationFullScreen on all other platforms.
*/
@property(nonatomic,assign) UIModalPresentationStyle modalPresentationStyle API_AVAILABLE(ios(3.2));iOS 13 的 presentViewController 默认有视差效果，模态出来的界面现在默认都下滑返回。
一些页面必须要点确认才能消失的，需要适配。如果项目中页面高度全部是屏幕尺寸，那么多出来的导航高度会出现问题。
// Swift
self.modalPresentationStyle = .fullScreen
// Objective-C
self.modalPresentationStyle = UIModalPresentationFullScreen;UISegmentedControl 默认样式改变
默认样式变为白底黑字，如果设置修改过颜色的话，页面需要修改
App启动过程中，部分View可能无法实时获取到frame
可能是为了优化启动速度，App 启动过程中，部分View可能无法实时获取到正确的frame
// 只有等执行完 UIViewController 的 viewDidAppear 方法以后，才能获取到正确的值，在viewDidLoad等地方 frame Size 为 0，例如：
[[UIApplication sharedApplication] statusBarFrame];其他参考：