Some adaptations of iOS13

According to the official website, all iPhone and iPad applications submitted to the App Store after April 2020 must be compiled with an SDK above iOS 13 and support full-screen iPhone Xs Max or 12.9-inch iPad Pro (3rd generation) and later versions design.

Starting April, 2020, all iPhone and iPad apps submitted to the App Store will need to be built with the iOS 13 SDK or later. They must also support the all-screen design of iPhone XS Max or the 12.9-inch iPad Pro (3rd generation), or later.

1. Private method KVC may cause a crash

In iOS 13 some method properties are not allowed to use  valueForKey, setValue:forKey: get or set private properties. The specific manifestation is that it will crash directly at runtime and prompt the following crash information: 

*** Terminating app due to uncaught exception 'NSGenericException', reason: 'Access to UISearchBar's _searchField ivar is prohibited. This is an application bug'

// 崩溃 api
UITextField *textField = [searchBar valueForKey:@"_searchField"];

// 替代方案 1，使用 iOS 13 的新属性 searchTextField
searchBar.searchTextField.placeholder = @"search";

// 替代方案 2，遍历获取指定类型的属性
- (UIView *)findViewWithClassName:(NSString *)className inView:(UIView *)view{
    Class specificView = NSClassFromString(className);
    if ([view isKindOfClass:specificView]) {
        return view;
    }

    if (view.subviews.count > 0) {
        for (UIView *subView in view.subviews) {
            UIView *targetView = [self findViewWithClassName:className inView:subView];
            if (targetView != nil) {
                return targetView;
            }
        }
    }
    
    return nil;
}

// 调用方法
 UITextField *textField = [self findViewWithClassName:@"UITextField" inView:_searchBar];
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---

// 崩溃 api
[searchBar setValue:@"取消" forKey:@"_cancelButtonText"];

// 替代方案，用同上的方法找到子类中 UIButton 类型的属性，然后设置其标题
UIButton *cancelButton = [self findViewWithClassName:NSStringFromClass([UIButton class]) inView:searchBar];
[cancelButton setTitle:@"取消" forState:UIControlStateNormal];
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// 崩溃 api。获取 _placeholderLabel 不会崩溃，但是获取 _placeholderLabel 里的属性就会
[textField setValue:[UIColor blueColor] forKeyPath:@"_placeholderLabel.textColor"];
[textField setValue:[UIFont systemFontOfSize:20] forKeyPath:@"_placeholderLabel.font"];

// 替代方案 1，去掉下划线，访问 placeholderLabel
[textField setValue:[UIColor blueColor] forKeyPath:@"placeholderLabel.textColor"];
[textField setValue:[UIFont systemFontOfSize:20] forKeyPath:@"placeholderLabel.font"];

// 替代方案 2
textField.attributedPlaceholder = [[NSAttributedString alloc] initWithString:@"输入" attributes:@{
    NSForegroundColorAttributeName: [UIColor blueColor],
    NSFontAttributeName: [UIFont systemFontOfSize:20]
}];
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