c ++如何从函数中的向量中删除对象

Question

I would like to remove objects from a vector. The vector is passed by reference, and I'm lost. I have tried brickList.erase(it) and also the combination erase remove, but I can't figure out the correct expression.

Would someone be so kind to help me on the commented line? In the general case with let's say 100 bricks with random positions.

#include "stdafx.h"

#include <iostream>
#include <vector>

class Brick {
private:
    int position;
public:
    Brick(int);
    int getPosition();
};
Brick::Brick(int p) : position(p) {};
int Brick::getPosition() { return position; }

void removeBricks(int a, int b, std::vector<Brick> &brickList) {
    std::vector<Brick>::iterator it;
    for (it = brickList.begin(); it != brickList.end(); ++it) {
        int currentPos = (*it).getPosition();
        if (currentPos >= a && currentPos <= b) {
            // here I need help to delete objects
        }
    }
}

int _tmain(int argc, _TCHAR* argv[])
{
    std::vector<Brick> myBricks;
    for (int i = 0; i<10; ++i) {
        Brick tmp_brick(i);
        myBricks.push_back(tmp_brick);
    }
    // delete all bricks with position between 3 and 5
    removeBricks(3, 5, myBricks);
    system("pause");
    return 0;
}

Answer 1

From your code

// delete all bricks with position between 3 and 5
//removeBricks(3, 5, myBricks);  // <-- replace this
myBricks.erase(myBricks.begin()+3,myBricks.begin()+5); // <--  with this

using the range based erase function. You don't need your removeBricks function at all really.

If you have to use removeBricks() function you could do it like this using the same function prototype.

void removeBricks(int a, int b, std::vector<Brick> &brickList) {
    // check a >= 0, a < b and b doesn't exceed length of brickList
    brickList.erase(brickList.begin()+a,brickList.begin()+b);
}

EDIT: seems that your notion of position does not refer to the array position of your items but the value of the member function of Brick . This should work for you.

void removeBricks(int a, int b, std::vector<Brick> &brickList) 
{
    std::vector<Brick>::iterator it;
    for (it = brickList.begin(); it != brickList.end(); /* DONT increment here*/) {
        int currentPos = (*it).getPosition();
        if (currentPos >= a && currentPos <= b) {
            // store the return value from erase!!
            it = erase(it);
        }
        else
        {
            // increment here rather than in the for loop incrementer
            it++;
        }
    }
}

You have to store the return value from erase because the iterator gets invalidated. The above should work for you although vector is not the best choice of container as erasing items can be slow due to the restructuring of the underlying array.