C++ structures and constructors

Question

A quick question about structures in C++ that I haven't managed to find the answer for:

I've read that the only difference between structures and classes is the member-visibility. So, does the compiler give the structure a default constructor? (and a default copyconstructor, destructor, and assignment operator aswell?) And can you define all of the above yourself?

Thanks, István

score 11 · Accepted Answer · answered Jun 20 '11 at 14:15

11

Yes, it does, and yes, you can.

answered Jun 20 '11 at 14:15

Andy Thomas

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score 1 · Answer 2 · edited Jun 20 '11 at 14:17

1

Yes to all your questions. The same holds true for classes.

edited Jun 20 '11 at 14:17

unwind

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answered Jun 20 '11 at 14:16

Matteo Italia

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score 1 · Answer 3 · answered Jun 20 '11 at 14:39

I've read that the only difference between structures and classes is the member-visibility.

Thats correct. Just to note that this includes inherited classes:

struct S1 { int m1; };
struct S2: S1 { int m2; };

In S2, both m2 and m1 have public visibility. And an S2* can be substituted where an S1* is expected.

score 0 · Answer 4 · edited May 23 '17 at 12:20

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. But only if you do not have your structure in a union.

e.g.

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

Credit goes to the answers in this question.

C++ structures and constructors

4 Answers4