C ++在向量中找到某些东西

Question

I have an vector like this:

struct RIFT_MONSTER_SPAWN
{
    DWORD dwWorldId;
    D3DXVECTOR3 vPos;
};

vector<RIFT_MONSTER_SPAWN> vecMSpawn;

As you can see it will hold 2 values dwWorldId and D3DXVECTOR3 vPos; vPos will hold x,y,z value.

Now what I want to do is looping true the vector and if the worldId matches the worldId that is beeing passed. It should return the vPos that is releated to the worldId .

If have use std::find find_all and count . But it always returns the error binary == no operator found which takes a left hand operator of type

So I am an bit stuck on this. Any help would be appreciated.

With kind regards.

Here is the code that is giving me problems

void CRiftMatch::GetMoverSpawnPoints(dwWorldId)
{
    std::vector<RIFT_MONSTER_SPAWN> vecSpawn = CRiftMng::GetInstance()->m_vecMSpawnPoint;
    std::vector<RIFT_MONSTER_SPAWN>::iterator it = std::find(vecSpawn.begin(), vecSpawn.end(), dwWorldId);
    OUTPUTDEBUGSTRING("\n GetMoverSpawn %d", *it);
}

m_vecMSpawnPoint is defined in .h file as

vector<RIFT_MONSTER_SPAWN> m_vecMSpawnPoint;

Also to fill it i am using this code

while (Lua.TableLoop(-2))
        {
            RIFT_MONSTER_SPAWN rSpawnPoint;
            rSpawnPoint.dwWorldId = static_cast<int>(CScript::GetDefineNum(Lua.GetFieldToString(-1, "dwWorldId")));
            rSpawnPoint.vPos.x = static_cast<float>(Lua.GetFieldToNumber(-1, "x"));
            rSpawnPoint.vPos.y = static_cast<float>(Lua.GetFieldToNumber(-1, "y"));
            rSpawnPoint.vPos.z = static_cast<float>(Lua.GetFieldToNumber(-1, "z"));

            m_vecMSpawnPoint.push_back(rSpawnPoint);
            Lua.Pop(1);
        }

Answer 1

You have to modify your struct to be able compare values during find:

struct RIFT_MONSTER_SPAWN
{
    DWORD dwWorldId;
    D3DXVECTOR3 vPos;

    bool operator () ( const RIFT_MONSTER_SPAWN & m ) const
    {
        return m.dwWorldId == dwWorldId;
    }
};

RIFT_MONSTER_SPAWN monsterToFind;
monsterToFind.dwWorldId = dwWorldId;

it = std::find_if( vecSpawn.begin(), vecSpawn.end(), monsterToFind);

---

Maybe just a type, but in your code, you have

void CRiftMatch::GetMoverSpawnPoints(dwWorldId)

but it should be

void CRiftMatch::GetMoverSpawnPoints(DWORD dwWorldId)

Answer 2

You could pass a predicate (which can be a lambda) to std::find_if so code

  auto it = std::find_if(vecSpawn.begin(), vecSpawn.end(),
                         [&] (const struct RIFT_MONSTER_SPAWN& sp) 
                            {return sp.dxWorldId == dwWorldIt;});

But in such a case I would simply use a for loop (because I find that more readable):

  int ix=0;
  for (auto&sp : vecSpawn) {
     if (sp.dxWorldId == dwWorldIt) 
        return vecSpawn.begin() + ix;
     ix++;
  }

Answer 3

With range/v3 , you may simply do

auto it = ranges::find(vecSpawn, dwWorldIt, &RIFT_MONSTER_SPAWN::dxWorldId);

else you have to use more verbose

auto it = std::find_if(vecSpawn.begin(), vecSpawn.end(),
                       [&](const RIFT_MONSTER_SPAWN& e) {
                           return e.dxWorldId == dwWorldIt;
                       });