没有默认构造函数的类

Question

Can we create an array of objects of the class not having default constructor, if yes then can anyone elaborate on how can we do this?

For following class for Abc a[10] in main(); is generating compiler error 'no matching function for call to `Abc::Abc()'

class Abc{
    private: 
           int x;
    public:
           Abc(int a){
           x = a;
           }
};

int main(){
    Abc a[10]; // Compilation would fail here, as it would look for default constructor
}

Answer 1

Can we create an array of objects of the class not having default constructor?

Yes, you can. You have to call one of the available constructors to initialize each of the members of the array. The only way to do that is to initialize the array with an initialization list:

Abc a[10] = { 1, 2, 3, 4, 5, 6, 7, 8, 9, 10};

In this case, it is enough to put integers in the array, because your Abc constructor is not explicit. This means you can do this:

Abc a = 42; // Calls A(42)

If it were explicit, you would have to say

Abc a[10] = { Abc(1), Abc(2), ..... };

Obviously this dosn't scale well, but it works OK for small arrays.

Answer 2

The problem is that if you define a constructor, of any kind, the compiler will not automatically generate a default constructor. You have to do it manually.