假设我们有一个带有纯虚方法(一个接口)的抽象基类 IBase
.
Say we have an abstract base class IBase
with pure virtual methods (an interface).
然后我们从基类派生CFoo
、CFoo2
.
Then we derive CFoo
, CFoo2
from the base class.
我们有一个知道如何使用 IBase 的函数.
And we have a function that knows how to work with IBase.
Foo(IBase *input);
在这些情况下通常的场景是这样的:
The usual scenario in these cases is like this:
IBase *ptr = static_cast<IBase*>(new CFoo("abc"));
Foo(ptr);
delete ptr;
但是最好避免指针管理,那么在这种情况下有没有办法使用引用?
But pointer management is better to be avoided, so is there a way to use references in such scenario?
CFoo inst("abc");
Foo(inst);
其中 Foo
是:
Foo(IBase &input);
是的.您不必向上转换您的对象.必要时,所有对派生类型的引用/指针都会隐式转换为基对象引用/指针.
Yes. You don't have to upcast your objects. All references/pointers to derived types are converted implicitly to base objects references/pointers when necessary.
所以:
IBase* ptr = new CFoo("abc"); // good
CFoo* ptr2 = static_cast<CFoo*>(ptr); // good
CFoo* ptr3 = ptr; // compile error
CFoo instance("abc");
IBase& ref = instance; // good
CFoo& ref2 = static_cast<CFoo&>(ref); // good
CFoo& ref3 = ref; // compile error
当您不得不向下转型时,如果您的类型是多态的,您可能需要考虑使用 dynamic_cast
.
When you have to downcast you may want to consider using dynamic_cast
, if your types are polymorphic.
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