Structure Constructor in C++?

Question

Can a struct have a constructor in C++?

I have been trying to solve this problem but not getting any syntax.

Answer 1

struct TestStruct {
        int id;
        TestStruct() : id(42)
        {
        }
};

Answer 2

In C++ the only difference between a class and a struct is that class-members are private by default, while struct-members default to public. So structures can have constructors, and the syntax is the same as for classes.

Answer 3

Yes. A structure is just like a class, but defaults to public:, in the class definition and when inheriting:

struct Foo
{
    int bar;

    Foo(void) :
    bar(0)
    {
    }
}

Considering your other question, I would suggest you read through some tutorials. They will answer your questions faster and more complete than we will.

Answer 4

Yes structures and classes in C++ are the same except that structures members are public by default whereas classes members are private by default. Anything you can do in a class you should be able to do in a structure.

struct Foo
{
  Foo()
  {
    // Initialize Foo
  }
};

Answer 5

Yes, but if you have your structure in a union then you cannot. It is the same as a class.

struct Example
{
   unsigned int mTest;
   Example()
   {
   }
};

Unions will not allow constructors in the structs. You can make a constructor on the union though. This question relates to non-trivial constructors in unions.

Answer 6

In C++, we can declare/define the structure just like class and have the constructors/destructors for the Structures and have variables/functions defined in it. The only difference is the default scope of the variables/functions defined. Other than the above difference, mostly you should be able to imitate the functionality of class using structs.

Answer 7

struct HaveSome
{
   int fun;
   HaveSome()
   {
      fun = 69;
   }
};

I'd rather initialize inside the constructor so I don't need to keep the order.