问"_GetVoiceEngine", referenced from:？

Xcode 调用c++方法,编译报错, "_GetVoiceEngine", referenced from: 是为什么呢?

代码如下, 该导的文件已经导入, 写的时候没错, 编译报错

gcloud_voice::GetVoiceEngine()->SetAppInfo("", "", openIDS.str().c_str());

gcloud_voice::GetVoiceEngine()->Init();