如何在C ++中通过引用复制对象？

Question

I have following case. That's what I'm trying to do:

std::vector < Shape > shapesArr;
Shape *shape = new Shape();
shape->someParam = someValue;
shapesArr.push_back( Shape );

// ...

Shape *shape2 = new Shape();
shape2 = shapesArr[ 0 ]; // <-- here I need a copy of that object to shapeA

delete[] shapesArr;
delete shape2; // <-- error, because it has already freed. It would be nice if I had a copy of shapesArr[ 0 ] in my shape2

How to properly copy that object to shape2? I need two copies of that object which will be stored in shapesArr[ 0 ] and shape2 separately.

Answer 1

You can use Shape *shape2 = new Shape(shapesArr[0]); to create a copy.

There are two errors in your code:

First:

std::vector < Shape > shapesArr;
Shape *shape = new Shape();
shape->someParam = someValue;
// you should push *shape, because Shape is just the class name
// and shape is a Shape* type pointer
// you can shapesArr.push_back( *shape );
shapesArr.push_back( Shape );

Second, you can't delete the vector, because you didn't new a vector, if you want to erase all the element in the vector, use shapesArr.clear() or shapesArr.erase(shapesArr.begin(),shapesArr.end());