NSString与Class之间的相互转换

Class NSClassFromString (NSString *aClassName);
NSString * NSStringFromClass (Class aClass);

NSString * NSStringFromProtocol (Protocol *proto);
Protocol *NSProtocolFromString (NSString *namestr);

NSString *NSStringFromSelector (SEL aSelector);
SEL NSSelectorFromString (NSString *aSelectorName);

// 还有一种转为char型的字符串接口：

const char* className = class_getName([yourObject class]);