问题
In C#, passing by reference is:
void MyFunction(ref Dog dog)
But in C++/CLI code examples I have seen so far, there is no use of ref but instead ^ symbol is used:
void MyFunction(Dog ^ dog)
Is the use of ^ symbol a direct replacement for ref when parameter passing? or does it have some other meaning I'm not aware of?
Additional Question: I also see a lot of:
Dog ^ myDog = gcnew Dog();
It looks like it's used like * (pointer) in C++.. Does it work similarly?
Thanks!
回答1:
If Dog is a reference type (class in C#) then the C++/CLI equivalent is:
void MyFunction(Dog^% dog)
If Dog is a value type (struct in C#) then the C++/CLI equivalent is:
void MyFunction(Dog% dog)
As a type decorator, ^ roughly correlates to * in C++, and % roughly correlates to & in C++.
As a unary operator, you typically still need to use * in C++/CLI where you use * in C++, but you typically need to use % in C++/CLI where you use & in C++.
回答2:
The ^ operator behaves similarly to a pointer in C++/CLI. The difference is that it's a garbage-collected pointer. So:
Dog ^ mydog = gcnew Dog();
is simply saying that we will new using the managed memory (gcnew) and pass the managed pointer back to mydog.
So:
void MyFunction(Dog ^ dog)
Is actually passing by address, not be reference, but they're kinda similar. If you want to pass by reference in C/C++ you do something like:
void MyFunction(Dog &dog);
in the function declaration. I assume it'll be the same for C++/CLI, but I've never tried it. I try not to use the ref's since it's not always clear that they are.
EDIT: Well, it's not the same, it's % not &, which makes sense they'd have to change that too. Stupid C++/CLI.
回答3:
From MSDN - ^ (Handle to Object on Managed Heap):
Declares a handle to an object on the managed heap.
And:
The common language runtime maintains a separate heap on which it implements a precise, asynchronous, compacting garbage collection scheme. To work correctly, it must track all storage locations that can point into this heap at runtime. ^ provides a handle through which the garbage collector can track a reference to an object on the managed heap, thereby being able to update it whenever that object is moved.
回答4:
The "^" symbol indicates that "Dog" is a CLR object, not a traditional C++ object such as "Dog*", which is a pointer to a C++ object Dog. This means that "Dog ^ dog" has the same meaning as "Dog dog" (not "ref Dog dog") in C#
来源：https://stackoverflow.com/questions/6616599/does-the-symbol-replace-cs-ref-in-parameter-passing-in-c-cli-code