CODEWITHSUNDEEP
c++
BPS1945
BPS1945

Reputation: 163

c++ convert from new to instance

There is a problem that confuses me

I created a new variable

Foo *a=new Foo();

Then I declared an Instance variable

Foo b;

Now I want to convert the new variable to the instance variable, so I did

b.setValue0(a->getValue0());
b.setValue1(a->getValue1());
b.setValue2(a->getValue2());

Is there an easier faster way to do this?

Upvotes: 0

Views: 57

Answers (3)

DML
DML

Reputation: 544

You can use copy constructor with a reference to a const parameter. It is const to guarantee that the copy constructor doesn't change it.

class Foo{
    public:
        . . .
        // copy constructor
        Foo(const Foo &b) 
        {
           value0 = b.value0;
           value1 = b.value1;
        }
}

//=== file main_program.cpp ====================================
. . .
Foo fooObj;                        // calls default constructor
Foo anotherFooObj = fooObj;        // calls copy constructor.

Upvotes: 0

πάντα ῥεῖ
πάντα ῥεῖ

Reputation: 1

"Is there an easier faster way to do this?"

You can declare an assignment operator for Foo

 Foo& operator=(const Foo&);

Thus you can write 

 b = *a;

The other option is to provide a copy constructor

 Foo(const Foo&);

This allows to initialize b directly

 Foo b(*a);

You should note that the compiler will automatically generate these operations for you, unless you declare any of these your own, or declare special constructors with paraneters.

Upvotes: 1

6502
6502

Reputation: 114461

You can use the copy constructor:

Foo b(*a);

assuming of course that copying the object is permitted.

Upvotes: 3

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