实例化 C++ 时遇到问题目标 C 的类别
我将 C++ 与 ObjectiveC 混合用于 Cocos2d (objective-C) 和 Box2D (C++) 项目。
我有以下 C++ 类：
class ActorListener : public b2ContactListener
{
public :
const b2Body* Owner;
ActorListener(const b2Body* owner);
~ActorListener();
virtual void BeginContact(b2Contact* contact);
virtual void EndContact(b2Contact* contact);
virtual void PreSolve(b2Contact* contact, const b2Manifold* oldManifold);
virtual void PostSolve(b2Contact* contact, const b2ContactImpulse* impulse);
};
我尝试使用以下内容进行初始化：（
在标头中）
ActorListener* Listener;
（在 mm 文件中）
Listener = new ActorListener(Body);
我收到错误：
Undefined symbols for architecture i386:
"vtable for ActorListener", referenced from:
ActorListener::ActorListener(b2Body const*)in ActorListener.o
ActorListener::ActorListener(b2Body const*)in ActorListener.o
ld: symbol(s) not found for architecture i386
collect2: ld returned 1 exit status
I'm mixing C++ with ObjectiveC for a Cocos2d (objective-C) and Box2D (C++) project.
I have the following C++ class:
class ActorListener : public b2ContactListener
{
public :
const b2Body* Owner;
ActorListener(const b2Body* owner);
~ActorListener();
virtual void BeginContact(b2Contact* contact);
virtual void EndContact(b2Contact* contact);
virtual void PreSolve(b2Contact* contact, const b2Manifold* oldManifold);
virtual void PostSolve(b2Contact* contact, const b2ContactImpulse* impulse);
};
Which I try to initialise with:
(in header)
ActorListener* Listener;
(in mm file)
Listener = new ActorListener(Body);
I get the error:
Undefined symbols for architecture i386:
"vtable for ActorListener", referenced from:
ActorListener::ActorListener(b2Body const*)in ActorListener.o
ActorListener::ActorListener(b2Body const*)in ActorListener.o
ld: symbol(s) not found for architecture i386
collect2: ld returned 1 exit status
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诀窍是让 XCode 使用 g++ 进行链接。您可以通过在链接行上包含 C++ 源文件（即使是假的、本质上是空的文件）或（我认为）通过显式链接 /usr/lib/libstdc++.6.dylib 来强制执行此操作。
The trick is to get XCode to use g++ to do the linking. You can force this either by including a C++ source file on the link line -- even a fake, essentially empty one -- or (I think) by explicitly linking with /usr/lib/libstdc++.6.dylib .
vtable 与类的第一个虚拟函数在同一文件中发出。在本例中，
~ActorListener()是第一个虚拟方法，因为b2ContactListener::~b2ContactListener()是虚拟的。您是否记得在某处定义ActorListener::~ActorListener()？The vtable is emitted in the same file as the first virtual function of the class. In this case,
~ActorListener()is the first virtual method, becauseb2ContactListener::~b2ContactListener()is virtual. Did you remember to defineActorListener::~ActorListener()somewhere?