How to initialize an array of struct in C++?

Question

I have the following struct in my C++ code (I am using Visual Studio 2010):

struct mydata
{
    string scientist;
    double value;
};

What I would like to do is to be able to initialize them in a quick way, similar to array initialization in C99 or class initialization in C#, something á la:

mydata data[] = { { scientist = "Archimedes", value = 2.12 }, 
                  { scientist = "Vitruvius", value = 4.49 } } ;

If this is not possible in C++ for an array of structs, can I do it for an array of objects? In other words, the underlying data type for an array isn't that important, it is important that I have an array, not a list, and that I can write initializers this way.

There is no reason why it shouldn't work... (btw that would be .scientist = ...) Have you tried? — fge
– fge, Commented Dec 16, 2011 at 13:03
@fge Yes, it's called aggregate initialisation and is further explained in detail here — pfabri
– pfabri, Commented Dec 10, 2017 at 11:12

Community · Accepted Answer · 2017-05-23 12:02:34Z

72

The syntax in C++ is almost exactly the same (just leave out the named parameters):

mydata data[] = { { "Archimedes", 2.12 }, 
                  { "Vitruvius", 4.49 } } ;

In C++03 this works whenever the array-type is an aggregate. In C++11 this works with any object that has an appropriate constructor.

edited May 23, 2017 at 12:02

CommunityBot

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answered Dec 16, 2011 at 13:03

Björn Pollex

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3 Comments

Lara Bailey Over a year ago

I thought that uniform initialization usually referred to the list-initialization form (i.e. without the =)? I couldn't find a reference for uniform initialization in the standard.

cjcurrie Over a year ago

@BjörnPollex It would not be a bad thing to re-mention, I think.

digitig Over a year ago

This appears to be a gcc extension. As far as I can make out, it's not standard C++ and is unlikely to work in other compilers. It doesn't work in Visual Studio, anyway.

Bhargav Rao · Accepted Answer · 2021-06-18 06:54:10Z

0

In my experience, we must set the array size of data and it must be at least as big as the actual initializer list :

//          ↓
mydata data[2] = { { "Archimedes", 2.12 }, 
                  { "Vitruvius", 4.49 } } ;

edited Jun 18, 2021 at 6:54

Bhargav Rao

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answered Jun 17, 2021 at 21:37

Gy_Fk

1

Comments

Sarath Govind · Accepted Answer · 2021-06-18 07:32:17Z

-3

The below program performs initialization of structure variable. It creates an array of structure pointer.

struct stud {
    int id;
    string name;
    stud(int id,string name) {
        this->id = id;
        this->name = name;
    }
    void getDetails() {
        cout << this->id<<endl;
        cout << this->name << endl;
    }
};

 int main() {
    stud *s[2];
    int id;
    string name;
    for (int i = 0; i < 2; i++) {
        cout << "enter id" << endl;
        cin >> id;
        cout << "enter name" << endl;
        cin >> name;
        s[i] = new stud(id, name);
        s[i]->getDetails();
    }
    cin.get();
    return 0;
}

answered Jun 18, 2021 at 7:32

Sarath Govind

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