Am I using std::map's find function correctly? Want to access class data

Question

So the following code compiles but i'm not sure if it's doing what I want it to do... (VS2010 for reference)

// Declarations

typedef std::map<unsigned int, QGF6::GameObject*> localMap;
localMap lMap;

// Code in a function that I might be using with the wrong logic:

lMap.find(p.id)->second->getPhysics()->setLinearVelocity(linVel);

Intended Logic:

Find the unsigned int value in the map that equals p.id(another unsigned int) then to that member of the map, access it's second data type(GameObject*) and do stuff.

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So the question is whether or not that should be working 'as intended' ? It compiles but as I'm having bugs with velocity I'm thinking it might be a misunderstanding of the std::map class.

Answer 1

That will work only if the searched item is actually present in the map. Otherwise using it will cause undefined behavior. You should use something like the following

 std::map<unsigned int, QGF6::GameObject*>::iterator itr = lMap.find(p.id);
 if(itr!= lMap.end()){ //found
  //use it
 }

or,

 QGF6::GameObject* obj = lMap[p.id];
 if( obj!=nulptr){
  //use it
 }