CODEWITHSUNDEEP
c++inheritance
Opeww
Opeww

Reputation: 21

How to set base class fields by copying, through method from derived class?

class Base{
public:
float a,b;
};

class Derived:public Base{
public:
int someInteger, otherInt;

void assignNthElement(vector<Base> &myArray,int i){
this=myArray[i-1];//??? How ???
}

void simpleMethodOfAssigningNthElement(vector<Base>&myArray,int i){
a=myArray[i-1].a;
b=myArray[i-1].b;
}


};

How to directly copy values describing Base class within derived class from myArray? Maybe it's better to do it like it's done in "simpleMethodOfAssigningNthElement"? Which is faster?

Upvotes: 1

Views: 80

Answers (3)

inkooboo
inkooboo

Reputation: 2954

You can use some C-hacks, but it is bad way. Best way is simpleMethodOfAssigningNthElement. If you want you can overload operator= for Derived class.

class Base{
public:
float a,b;
};

class Derived : public Base{
public:
    int someInteger, otherInt;

    void assignNthElement(vector<Base> &myArray,int i){
        this = myArray[i-1];// It's OK now
    }

    const Derived & operator=(const Base &base){
        a=base.a;
        b=base.b;
    }

};

Upvotes: 0

Alok Save
Alok Save

Reputation: 206646

You cannot assign an Base class object to an Derived class object as in assignNthElement() that will give you a compilation error.

Note that the reverse is allowed, ie: you can assign an Derived class object to an Base class object, but that would end up slicing up the members of the derived class object. The phenomenon is called Object Slicing.

Upvotes: 1

Asha
Asha

Reputation: 11232

You can not do it the way you are trying in assignNthElement, it needs to be implemented like simpleMethodOfAssigningNthElement only.

Upvotes: 1

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