如何在C++中通過引用複製對象？

Question

我有以下情況。這就是我想要做的：

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 

如何正確地將該對象複製到shape2？我需要該對象的兩個副本，它們將分別存儲在shapesArr [0]和shape2中。

Answer 1

您可以使用Shape *shape2 = new Shape(shapesArr[0]);來創建副本。

有兩個錯誤在你的代碼：

第一：

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); 

其次，你不能刪除向量，因爲你沒有新的載體，如果你想刪除所有向量中的元素，使用shapesArr.clear()或shapesArr.erase(shapesArr.begin(),shapesArr.end());