How many constructors can an inherited class have?

Question

When I'm trying to create multiple constructors for an inherited class, I have an error throw out saying: No matching function call to A::A(). My codes are shown as below:

class A{  
public:  
    int a;  
    int b;  
    A(int i, int k) : a(i), b(k){  

    };  

};  

class B : public A{  
public:  
    B(){  

    };  
    B(int i, int k) : A(i, k){  
    };  


};  

Answer 1

B() {}  

is equivalent to

B() : A() {}

Since A doesn't have a default constructor, that is a compile time error.

You can fix it by:

1. Adding a default constructor to A , or

2. By changing the implementation of B 's default constructor to use the existing constructor of A .

    B() : A(0, 0) {} 

Answer 2

How many constructors can an inherited class have?

The language does not impose a limit on the number of constructors whether the class inherits another or not (except if you inherit a class with no non-deleted constructors, then the child also cannot have any non-deleted constructors).

The implementation may be constrained in practice. The minimum number of maximum supported member declarations - which includes the constructors - for a single class recommended by the standard is 4096. Being a recommendation means that neither lower nor higher supported maximum affects whether an implementation may be considered to be standard compliant.

No matching function call to A::A()

This is because you're trying to default initialise the base class sub object, but the base class is not default-initialisable.

There are two possible solutions:

1. Declare a default constructor so that A is default initialisable, or
2. Initialise the base class sub object using the non-default constructor. Example:

---

B(): A(42, 1337) {}