c++ - 确保const指针成员变量的constness

Question

为什么这段代码编译顺利？

class myvector
{
public:
    myvector()
    {
        begin = new double[10];
        end = begin+10;
    }
    ~myvector()
    {
        delete[] begin;
    }

    double *begin;
    double *end;
};

class VectorWorker
{
public:
    VectorWorker(){}
    void doWork(const myvector *v)
    {
        for (int i=0;i<10;i++)
            v->begin[i] = i; // I don't want this to compile! I'd prefer compiler says me I can't modify v->begin
    }

    void doWork2(const myvector *const v) const
    {
        for (int i=0;i<10;i++)
            v->begin[i] = i; // I don't want this to compile!  I'd prefer compiler says me I can't modify v->begin
    }

    void doWork3(const myvector &v)
    {
        for (int i=0;i<10;i++)
            v.begin[i] = i; // I don't want this to compile!  I'd prefer compiler says me I can't modify v->begin
    }
};

int main(int, char*[])
{

    myvector x;
    VectorWorker work;
    work.doWork(&x);

    work.doWork2(&x);
    work.doWork3(x);

    return 0;
}

我希望将 const myvector *v 传递给 VectorWorker::doWork 方法，应该确保我保留 myvector 中的变量完好无损，但实际上它们被修改了。我如何确定 doWork 方法允许只读操作？

实际上我无法将 double *begin 和 double *end 变量修改为 const double * 因为它们来自第三方-党库。但是，即使通过 const pointer，我如何确保它们在通过它们所属的类的实例时保持完好无损？

代码在coliru中可用:http://coliru.stacked-crooked.com/a/bb43fbebebdb5872

Answer 1

使用访问器:

class myvector
{
public:
    //previous code

    const double* get_begin() const { return begin; }
    const double* get_end() const { return end; }
    double* get_begin() { return begin; }
    double* get_end() { return begin; }
private:
    double *begin;
    double *end;
};