C ++数据成员。 目标：在构造函数中初始化然后不理会，const在这里可以工作吗？

Question

I have the following

    struct dweDMPair {
        const dweller   *occu;
        const double    sqDM;
        float   prob;
        dweDMPair(dweller *inOccu, double sqdm) : occu(inOccu), sqDM(sqdm) {}       };

I want to return an array of pointers to these objects but desire that they should not be accidentally deleted by the client. Or, err, maybe not, just trying this design iteration.

My question is, is there a (very concise and neat) way of specifying (as I have illustrated with a const prefix) that members are only ever assigned in the constructor?

I know private/public and interface/methods could sort this, but humour me, how far can the const keyword be exploited?

_ EDIT _

Nawaz, my goal is simply to initialize 2 of the 3 data members once only, in the constructor. Then I can export this instance as a const dweDMPair *ptrToVal so that the client cannot then call delete- because that won't work on pointers to const instances will it? The client will then proceed to give their own value for the third member prob . yeah, I know functions enforce protection but I want it faster.

The members can't be static but instance members. In case you were wondering..

Answer 1

Yes, const does what you want. Note that what you do in the constructor initializer list is not assignment, it's initialization. You can't assign to const objects, but you can initialize them with a value. Also, regardless of making them const, you might want to consider encapsulating these members in a class as private members. It's not much more typing, but it does improve maintainability.

Edit:

To define const pointer you do:

Type * const member;

not

const Type* member;

the second syntax is pointer to const type, not const pointer.

Answer 2

You clarify that what you really want is:

Then I can export this instance as a const dweDMPair *ptrToVal so that the client cannot then call delete- because that won't work on pointers to const instances will it?

Delete can be called on pointers to const instances and it can be called on objects which contain const members. This use of const will not help you reach your goal.

Some example code that compiles without complaint:

struct dweller {
};

 struct dweDMPair {
        const dweller   *occu;
        const double    sqDM;
        float   prob;
        dweDMPair(dweller *inOccu, double sqdm) : occu(inOccu), sqDM(sqdm) {}       
 };

int main() {

    dweDMPair const* p = new dweDMPair(NULL, 3.14);

    delete p;
}

You might want to further clarify your end-goal (possibly in another question if it would change this one too much).