英文:
C++ API design shared_ptr and calling into functions
问题
I have similar C++ code to this:
struct Data { /* ... */ }
int SomeFunction1(const Data& data) { return 0; }
int SomeFunction2(std::shared_ptr<Data>& data) { return 0; } // this is non-const though
int SomeFunction3(const Data* data) { return 0; } // possibility of receiving nullptr
int main()
{
auto data = std::make_shared<Data>(); /* initialization somehow */;
return SomeFunction1(*data); // (1) call get and dereference the pointer
return SomeFunction2(data); // (2) create an API that accepts the shared pointer
return SomeFunction3(data) // (3) create an API that accepts raw pointers
}
Please, ignore for the sake of simplicity that I can use a unique_ptr in this specific example.
To me, (1) seems preferable, but I am wondering whether the code at the caller *data is common or rather some kind of design smell?
英文:
I have similar C++ code to this:
struct Data { /* ... */ }
int SomeFunction1(const Data& data) { return 0; }
int SomeFunction2(std::shared_ptr<Data>& data) { return 0; } // this is non-const though
int SomeFunction3(const Data* data) { return 0; } // possibility of receiving nullptr
int main()
{
auto data = std::make_shared<Data>(); /* initialization somehow */;
return SomeFunction1(*data.get()); // (1) call get and dereference the pointer
return SomeFunction2(data); // (2) create an API that accepts the shared pointer
return SomeFunction3(data.get()) // (3) create an API that accepts raw pointers
}
Please, ignore for the sake of simplicity that I can use a unique_ptr in this specific example.
To me, (1) seems preferable, but I am wondering whether the code at the caller *data.get() is common or rather some kind of design smell?
答案1
得分: 1
是的，shared.get() 通常并不表示一切都顺利。但是，在你的示例中，你不需要使用 get()，因为 std::shared_ptr 重载了 operator*，所以你可以简单地写成 SomeFunction1(*data)。
如果该函数不共享对象的所有权，这是首选的做法，这似乎是你的情况。否则，你将不得不复制 std::shared_ptr 对象。
英文:
Yes, shared.get() is not usually an indicator that everything is going well. However, in your example, you don't need get() because std::shared_ptr overloads operator*, so you can simply say SomeFunction1(*data).
This is preferably if the function does not take shared ownership of the object, which seems to be the case. Otherwise you would have to copy the std::shared_ptr object.
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