1. Class object_getClass(id obj)

获取isa指向的class

  NSPerson *person = [[NSPerson alloc] init];
  NSLog(@"%p %p",
              object_getClass(person),
              object_getClass(object_getClass(person))
);

//log
2020-08-29 18:13:25.156169+0800 runtime_API[13610:390470] 0x1000020f0 0x1000020c8

2. Class object_setClass(id obj, Class cls)

设置isa指向的class

  NSPerson *person = [[NSPerson alloc] init];
  object_setClass(person, NSCar.class);
  NSLog(@"%@",        object_setClass(person, NSCar.class));
  [person run];

// log
2020-08-29 18:21:24.521334+0800 runtime_API[13712:397596] NSCar
2020-08-29 18:21:24.521394+0800 runtime_API[13712:397596] -[NSCar run]

3. BOOL object_isClass(id obj)

判断一个oc对象是否class

        NSLog(@"%d %d %d",object_isClass(person),
              object_isClass(object_getClass(person)),
              object_isClass(object_getClass(object_getClass(person)))
              );

//log
2020-08-29 19:17:35.832826+0800 runtime_API[14234:426760] 0 1 1

4.1. Ivar class_getInstanceVariable(Class cls, const char * name)

获取示例变量信息

4.2. id object_getIvar(id obj, Ivar ivar)

获取成员变量的值

4.3. void object_setIvar(id obj, Ivar ivar, id value)

设置成员变量的值

4.4. void object_setIvarWithStrongDefault(id obj, Ivar ivar, id value)

设置成员变量的值(默认strong)

    //获取示例变量信息
    Ivar age_ivar = class_getInstanceVariable(NSPerson.class, "_age");
    const char *age_name = ivar_getName(age_ivar);
    const char *age_type = ivar_getTypeEncoding(age_ivar);
    NSLog(@"%s %s", age_name,age_type);
    
    //设置和获取成员变量的值

    //age
    object_setIvar(person, age_ivar, (__bridge id)(void *)27);
    id age = object_getIvar(person, age_ivar);
    NSLog(@"%d %d %@",person.age, (int)age,[person valueForKey:@"_age"]);
    
    //name
    Ivar name_ivar = class_getInstanceVariable(NSPerson.class, "_name");
    object_setIvar(person, name_ivar, @"bien");
    id name = object_getIvar(person, name_ivar);
    NSLog(@"%@ %@ %@",name,person.name,[person valueForKey:@"_name"]);

    //设置成员变量的值(默认strong)
    object_setIvarWithStrongDefault(person, name_ivar, @"wbn");
    NSLog(@"%@",person.name);

    
    //log
2020-08-29 20:23:18.234092+0800 runtime_API[15160:476832] _age i
2020-08-29 20:23:18.234382+0800 runtime_API[15160:476832] 27 27 27
2020-08-29 20:23:18.234551+0800 runtime_API[15160:476832] bien bien bien
2020-08-29 20:40:01.942927+0800 runtime_API[15301:488642] wbn

ARC不可用

id  object_copy(id obj, size_t size)   OBJC_ARC_UNAVAILABLE;
id  object_dispose(id obj)  OBJC_ARC_UNAVAILABLE;
Ivar object_setInstanceVariable(id obj, const char * name, void * value)
Ivar object_setInstanceVariableWithStrongDefault(id obj,const char * name,void * value)
Ivar object_getInstanceVariable(id obj, const char * name, void * * outValue)