CODEWITHSUNDEEP
c++
user1086635
user1086635

Reputation: 1544

static_cast class to another class?

I want to convert a class to another class. I'm trying to use static_cas which almost always work for me, why doesn't it work in the following?

struct Mouse
{
    Mouse() {}
    // .......
};

struct Mice
{
    Mice() {}
    // .........
};

int main()
{
    Mouse mouse;
    Mice mice = static_cast<Mice>(mouse);
}

Upvotes: 2

Views: 4667

Answers (2)

Jon Hanna
Jon Hanna

Reputation: 113242

Because not only is mouse not an instance of Mice, but it can't possibly be.

struct SomeBase
{
  //...
};
struct SomeDerived : SomeBase
{
  //...
};
struct Unrelated
{
  //...
};

SomeBase * b;
SomeDerived * d;
Unrelated * r;

//....

b = static_cast<SomeBase *>(d); //allowed, safe
d = static_cast<SomeDerived *>(b); //allowed, unsafe
r = static_cast<Unrelated *>(d); //not allowed, what is it even meant to do?

Upvotes: 1

UncleBens
UncleBens

Reputation: 41331

You can only cast an instance of Mouse into Mice if Mice has a constructor accepting Mouse, or Mouse has an operator Mice (latter is not particularly recommended).

Upvotes: 3

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