如何在公共类方法中初始化公共变量

Question

我有一个公共类，我在其中创建了一个数组，这个数组从构造函数中获取它的大小，并且需要在其他函数中使用（包括 int main）。因此变量必须是公开的。我的代码看起来是这样的：

class myclass {
    public:
    int parameter1;
    int parameter2;
    myclass(int p, int p2) {
        parameter1 = p;
        parameter2 = p2;
    }
    void makeArray() {
        int array[parameter1][parameter2]; //I want this array to be public as the next method needs access to it
    }
    void otherFunction() {
        array[1][2] = 5; //just an example of what i need to do
    }
}

Answer 1

这是做同样事情的更优化的方式：

class myclass {
    public:
    int parameter1;
    int parameter2;
    int *array;
    myclass(int p1, int p2) {
        parameter1 = p1;
        parameter2 = p2;
    }
    void makeArray() {
        array = new int[parameter1*parameter2];
    }
    void otherFunction() {
        // ary[i][j] is then rewritten as ary[i*sizeY+j]
        array[1*parameter2+2] = 5;
    }
};
int main()
{
    int sizeX = 5;
    int sizeY = 5;

    myclass m1(sizeX,sizeY);
    m1.makeArray();
    m1.otherFunction();
    cout << m1.array[1*sizeY+2] << endl;
    return 0;
}

Answer 2

查看如何使用指针和动态内存..

做你想做的事情是这样的：

class myclass {
    public:
    int parameter1;
    int parameter2;
    int **a;

    myclass(int p, int p2) {
        parameter1 = p;
        parameter2 = p2;
        a = nullptr;
    }

    ~myclass() {
        // TODO: delete "a"
    }

    void makeArray() {
        // TODO: delete "a" if it has already been allocated

        a = new *int[parameter1];
        for (int i = 0; i < parameter1; ++i) {
          a[i] = new int[parameter2];
        }
    }

    void otherFunction() {
        // TODO: check that "a" has already been allocated
        a[1][2] = 5; //just an example of what i need to do
    }
}

你也可以在构造函数中分配数组，因为你已经传入了必要的信息。