1，動態創建對象

1.1 ?id class_createInstance ( Class cls, size_t ?extraBytes );

1.2 ?id objc_constructInstance ( Class cls, void *bytes );

1.3 void * objc_destructInstance ( id obj ); //銷毀一個實例

2,把父類對象轉換為子類對象

NSObject *a = [[NSObject alloc] init];

id newB = object_copy(a, class_getInstanceSize(MyClass.class));

object_setClass(newB, MyClass.class);

object_dispose(a);

//MyClass繼承自NSObject。

3，讀寫對象的實例變量

3.1 修改實例變量的值

Ivar object_setInstanceVariable ( id obj, const char *name, void *value );

void object_setIvar ( id obj, Ivar ivar, id value );

3.2 獲取實例變量的值

Ivar object_getInstanceVariable ( id obj, const char *name, void **outValue );

id object_getIvar ( id obj, Ivar ivar );

3.3 獲取對象的類

Class object_getClass ( id obj );

3.4 設置對象的類

Class object_setClass ( id obj, Class cls );

3.5 返回對象的類名

const char * object_getClassName ( id obj );