/*
 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));

要改会原来模态视图样式，我们只需要把UIModalPresentationStyle@H_403_4@设置为UIModalPresentationFullScreen@H_403_4@即可。

ViewController *vc = [[ViewController alloc] init];
vc.title = @"presentVC";
UINavigationController *nav = [[UINavigationController alloc] initWithRootViewController:vc];
nav.modalPresentationStyle = UIModalPresentationFullScreen;
[self.window.rootViewController presentViewController:nav animated:YES completion:nil];

[_textField setValue:[UIColor redColor] forKeyPath:@"_placeholderLabel.textColor"];
[_textField setValue:[UIFont systemFontOfSize:14] forKeyPath:@"_placeholderLabel.font"];

_textField.attributedPlaceholder = [[NSAttributedString alloc] initWithString:@"姓名" attributes:@{NSFontAttributeName:[UIFont systemFontOfSize:14],NSForegroundColorAttributeName:[UIColor redColor]}];