Usage problem on std::unordered_map

[lucky6969b]

There is an error saying that unordered_map has no associated operator '->'
Any ideas why?
Thanks
Jack

#ifndef _OGREDETOURCROWDBASE_H_
#define _OGREDETOURCROWDBASE_H_

class OgreDetourCrowdBase {
public:
    virtual Ogre::Real getAgentHeight(void) = 0;  
    virtual Ogre::Real getAgentRadius(void) = 0;
    virtual int getNbAgents(void) { return 0; }
    virtual int getMaxNbAgents(void) { return 0; }
};


#endif

std::unordered_map<std::string, OgreDetourCrowdBase*> mDetourCrowd;

OgreDetourCrowdBase *detourCrowd = new OgreDetourCrowd(mRecast);
OgreDetourCrowdBase *detourCrowdCB = new OgreDetourCrowdCB(mRecastCB);
OgreDetourCrowdBase *detourCrowdVNA = new OgreDetourCrowdVNA(mRecastVNA);
OgreDetourCrowdBase *detourCrowdLorry = new OgreDetourCrowdLorry(mRecastLorry);

mDetourCrowd["Worker"] = detourCrowd;
mDetourCrowd["CB"] = detourCrowdCB;
mDetourCrowd["VNA"] = detourCrowdVNA;
mDetourCrowd["Lorry"] = detourCrowdLorry;

ObjectBase *OgreRecastApplication::createOperators(Ogre::String name, Ogre::Vector3 position) {
	if(mDetourCrowd["Worker"]->getNbAgents() >= mDetourCrowd["Worker"]->getMaxNbAgents()) {
        Ogre::LogManager::getSingletonPtr()->logMessage("Error: Cannot create crowd agent for new Worker. Limit of "+Ogre::StringConverter::toString(mDetourCrowd->getMaxNbAgents())+" reached", Ogre::LML_CRITICAL);
        throw new Ogre::Exception(1, "Cannot create crowd agent for new Worker. Limit of "+Ogre::StringConverter::toString(mDetourCrowd->getMaxNbAgents())+" reached", "OgreRecastApplication::getOrCreateCharacter("+name+")");
    }

     
    ObjectBase *worker = new Worker(name, mSceneMgr, mDetourCrowd, mDebugDraw, position);
    mObjects.push_back(worker);
    return worker;

}

Error 1 error C2819: type 'std::tr1::unordered_map<_Kty,_Ty>' does not have an overloaded member 'operator ->' e:\jacky\documents\visual studio 2010\projects\ogrecrowd\ogrecrowd\samples\src\ogrerecastapplication.cpp 379 1 OgreRecast
Error 2 error C2039: 'getMaxNbAgents' : is not a member of 'std::tr1::unordered_map<_Kty,_Ty>' e:\jacky\documents\visual studio 2010\projects\ogrecrowd\ogrecrowd\samples\src\ogrerecastapplication.cpp 379 1 OgreRecast
Error 3 error C2819: type 'std::tr1::unordered_map<_Kty,_Ty>' does not have an overloaded member 'operator ->' e:\jacky\documents\visual studio 2010\projects\ogrecrowd\ogrecrowd\samples\src\ogrerecastapplication.cpp 380 1 OgreRecast
Error 4 error C2039: 'getMaxNbAgents' : is not a member of 'std::tr1::unordered_map<_Kty,_Ty>' e:\jacky\documents\visual studio 2010\projects\ogrecrowd\ogrecrowd\samples\src\ogrerecastapplication.cpp 380 1 OgreRecast
Error 5 error C2664: 'Worker::Worker(Ogre::String,Ogre::SceneManager *,OgreDetourCrowd *,bool,Ogre::Vector3)' : cannot convert parameter 3 from 'std::tr1::unordered_map<_Kty,_Ty>' to 'OgreDetourCrowd *' e:\jacky\documents\visual studio 2010\projects\ogrecrowd\ogrecrowd\samples\src\ogrerecastapplication.cpp 384 1 OgreRecast
....
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