这是一个简单的类:#import"One.h"#import"Two.h"@implementationDataFileRegistrarstaticNSMutableDictionary*elementToClassMapping;+(void)load{[selfregisterClass:[Oneclass]forElement:@"one"];[selfregisterClass:[Twoclass]forElement:@"two"];}+(void)registerClass:(Class)classforElement:(NSString*)element{if(!ele