In iOS 13, we can not use KVC(valueForKey:,?setValue:forKey:) to access some private APIs, it causes the crash of?UISearchBar (QMUI),?UINavigationBar (QMUI)?and?UITabBar (QMUI).
以下記錄 iOS 13 系統(tǒng)禁止通過 KVC 訪問的幾種實現(xiàn)方式：
UITextField
UITextField *textField = [UITextFieldnew];[textFieldvalueForKey:@"_placeholderLabel"];
系統(tǒng)的 UITextField 重寫了?valueForKey:?攔截了外部的取值，實現(xiàn)如下:
@implementationUITextField- (id)valueForKey:(NSString*)key{if([keyisEqualToString:@"_placeholderLabel"]) {? ? ? ? [NSExceptionraise:NSGenericExceptionformat:@"Access to UITextField's _placeholderLabel ivar is prohibited. This is an application bug"];? ? }? ? [supervalueForKey:key];}@end
簡單解決：
去掉下劃線即可?[textField valueForKey:@"placeholderLabel"];
UISearchBar
UISearchBar *bar = [UISearchBarnew];[barsetValue:@"test"forKey:@"_cancelButtonText"]UIView *searchField = [barvalueForKey:@"_searchField"];
根據(jù) KVC 的實現(xiàn)，會先去找名為 set_cancelButtonText 的方法，所以系統(tǒng)內(nèi)部重寫了這個方法，什么事都不干，專門用來攔截 KVC，實現(xiàn)如下：
- (void)set_cancelButtonText:(NSString*)text {? ? [NSExceptionraise:NSGenericExceptionformat:@"Access to UISearchBar's set_cancelButtonText: ivar is prohibited. This is an application bug"];? ? [self_setCancelButtonText];}
攔截 _searchField：
- (void)_searchField {? ? [NSExceptionraise:NSGenericExceptionformat:@"Access to UISearchBar's _searchField ivar is prohibited. This is an application bug"];? ? [selfsearchField];}
簡單解決：
直接調(diào)用?_setCancelButtonText,?searchField
根據(jù)上面提到的原理，這里提供一種全局繞過這個禁止的方法供參考。
請注意：這只是一種臨時的參考方案，我們?不推薦?開發(fā)者這么做， 因為訪問私有屬性會帶來了不確定和不穩(wěn)定性，少了蘋果的警告會讓你無節(jié)制去訪問使用各種屬性，隨著系統(tǒng)的升級這私有屬性會面臨改動和失效的風(fēng)險。
@implementationNSException(DisableUIKVCAccessProhibited)+ (void)load{staticdispatch_once_tonceToken;dispatch_once(&onceToken, ^{MethodoriginalMethod =class_getClassMethod(self,@selector(raise:format:));MethodswizzlingMethod =class_getClassMethod(self,@selector(sw_raise:format:));method_exchangeImplementations(originalMethod, swizzlingMethod);? ? ? ? ? ? });}+ (void)sw_raise:(NSExceptionName)raiseformat:(NSString*)format, ... {if(raise==NSGenericException&& [formatisEqualToString:@"Access to%@'s%@ivar is prohibited. This is an application bug"]) {return;? ? }va_listargs;va_start(args, format);NSString*reason =? [[NSStringalloc]initWithFormat:formatarguments:args];? ? [selfsw_raise:raiseformat:reason];va_end(args);}@end
