jeck猫
可以通过class_addProperty()以下方式向类添加形式属性：BOOL class_addProperty(Class cls, const char *name, const objc_property_attribute_t *attributes, unsigned int attributeCount)前两个参数是不言自明的。第三个参数是属性的属性的阵列，并且每个属性特性是一个名称-值对，其遵循的Objective-C 型编码对声明的属性。请注意，文档中仍然提到了逗号分隔的字符串，用于属性属性的编码。逗号分隔的字符串中的每个段均由一个objc_property_attribute_t实例表示。此外，objc_property_attribute_t除了的通用@类型编码外，还接受类名称id。这里有一个程序，动态地增加了一个叫做物业的初稿name到已被称为实例变量类_privateName：#include <objc/runtime.h>#import <Foundation/Foundation.h>@interface SomeClass : NSObject { NSString *_privateName;}@end@implementation SomeClass- (id)init { self = [super init]; if (self) _privateName = @"Steve"; return self;}@endNSString *nameGetter(id self, SEL _cmd) { Ivar ivar = class_getInstanceVariable([SomeClass class], "_privateName"); return object_getIvar(self, ivar);}void nameSetter(id self, SEL _cmd, NSString *newName) { Ivar ivar = class_getInstanceVariable([SomeClass class], "_privateName"); id oldName = object_getIvar(self, ivar); if (oldName != newName) object_setIvar(self, ivar, [newName copy]);}int main(void) { @autoreleasepool { objc_property_attribute_t type = { "T", "@\"NSString\"" }; objc_property_attribute_t ownership = { "C", "" }; // C = copy objc_property_attribute_t backingivar = { "V", "_privateName" }; objc_property_attribute_t attrs[] = { type, ownership, backingivar }; class_addProperty([SomeClass class], "name", attrs, 3); class_addMethod([SomeClass class], @selector(name), (IMP)nameGetter, "@@:"); class_addMethod([SomeClass class], @selector(setName:), (IMP)nameSetter, "v@:@"); id o = [SomeClass new]; NSLog(@"%@", [o name]); [o setName:@"Jobs"]; NSLog(@"%@", [o name]); }}其（修剪后的）输出：SteveJobs应该更加仔细地编写getter和setter方法，但这足以作为如何在运行时动态添加形式属性的示例。