void objc_setAssociatedObject(id object, const void *key, id value, objc_AssociationPolicy policy) { _object_set_associative_reference(object, (void *)key, value, policy);}

typedef OBJC_ENUM(uintptr_t, objc_AssociationPolicy) { OBJC_ASSOCIATION_ASSIGN = 0,  /**< Specifies a weak reference to the associated object. */ OBJC_ASSOCIATION_RETAIN_NONATOMIC = 1, /**< Specifies a strong reference to the associated object.      * The association is not made atomically. */ OBJC_ASSOCIATION_COPY_NONATOMIC = 3, /**< Specifies that the associated object is copied.      * The association is not made atomically. */ OBJC_ASSOCIATION_RETAIN = 01401, /**< Specifies a strong reference to the associated object.      * The association is made atomically. */ OBJC_ASSOCIATION_COPY = 01403  /**< Specifies that the associated object is copied.      * The association is made atomically. */};

void _object_set_associative_reference(id object, void *key, id value, uintptr_t policy) { // retain the new value (if any) outside the lock. ObjcAssociation old_association(0, nil); id new_value = value ? acquireValue(value, policy) : nil; { AssociationsManager manager; AssociationsHashMap &associations(manager.associations()); disguised_ptr_t disguised_object = DISGUISE(object);//得到對(duì)象地址 if (new_value) {  // break any existing association.  AssociationsHashMap::iterator i = associations.find(disguised_object);//首先通過(guò)對(duì)象的地址獲取對(duì)象的hashmap  if (i != associations.end()) {//判斷是否已經(jīng)存在，已經(jīng)存在  // secondary table exists  ObjectAssociationMap *refs = i->second;//取值，對(duì)應(yīng)的map  ObjectAssociationMap::iterator j = refs->find(key);//通過(guò)key查找  if (j != refs->end()) {//如果已經(jīng)存在   old_association = j->second;//取到原來(lái)老的值,以便后邊對(duì)其釋放   j->second = ObjcAssociation(policy, new_value);//存儲(chǔ)新的值  } else {//不存在   (*refs)[key] = ObjcAssociation(policy, new_value);  }  } else {//如果不存在,創(chuàng)建一個(gè)  // create the new association (first time).  ObjectAssociationMap *refs = new ObjectAssociationMap;  associations[disguised_object] = refs;  (*refs)[key] = ObjcAssociation(policy, new_value);  object->setHasAssociatedObjects();  } } else {//不存在則創(chuàng)建一個(gè)  // setting the association to nil breaks the association.  AssociationsHashMap::iterator i = associations.find(disguised_object);  if (i != associations.end()) {  ObjectAssociationMap *refs = i->second;  ObjectAssociationMap::iterator j = refs->find(key);  if (j != refs->end()) {   old_association = j->second;   refs->erase(j);  }  } } } // release the old value (outside of the lock). if (old_association.hasValue()) ReleaseValue()(old_association);}

id objc_getAssociatedObject(id object, const void *key) { return _object_get_associative_reference(object, (void *)key);}

id _object_get_associative_reference(id object, void *key) { id value = nil; uintptr_t policy = OBJC_ASSOCIATION_ASSIGN; { AssociationsManager manager; AssociationsHashMap &associations(manager.associations()); disguised_ptr_t disguised_object = DISGUISE(object); AssociationsHashMap::iterator i = associations.find(disguised_object); if (i != associations.end()) {  ObjectAssociationMap *refs = i->second;  ObjectAssociationMap::iterator j = refs->find(key);  if (j != refs->end()) {  ObjcAssociation &entry = j->second;  value = entry.value();  policy = entry.policy();  if (policy & OBJC_ASSOCIATION_GETTER_RETAIN) {   objc_retain(value);  }  } } } if (value && (policy & OBJC_ASSOCIATION_GETTER_AUTORELEASE)) { objc_autorelease(value); } return value;}