Inheriting constructors

Question

Why does this code   class A       public           explicit A int x         class B  public A       int main void        B  b   new B 5       delete b      Result in these errors    main cpp  In function    int main       main cpp 13  error  no matching function for call to    B  B int     main cpp 8  note  candidates are  B  B   main cpp 8  note                  B  B const B     Shouldn t B inherit A s constructor    this is using gcc

User · Answer

This is straight from Bjarne Stroustrup s page   If you so choose  you can still shoot yourself in the foot by inheriting constructors in a derived class in which you define new member variables needing initialization   struct B1       B1 int          struct D1   B1       using B1  B1     implicitly declares D1 int      int x      void test         D1 d 6         Oops  d x is not initialized     D1 e           error  D1 has no default constructor

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How about using a template function to bind all constructors   template  lt class    T gt  Derived T    t    Base t

User · Answer

If your compiler supports C  11 standard  there is a constructor inheritance using using  pun intended   For more see Wikipedia C  11 article  You write   class A       public           explicit A int x         class B  public A        using A  A       This is all or nothing - you cannot inherit only some constructors  if you write this  you inherit all of them  To inherit only selected ones you need to write the individual constructors manually and call the base constructor as needed from them   Historically constructors could not be inherited in the C  03 standard  You needed to inherit them manually one by one by calling base implementation on your own

User · Answer

This is straight from Bjarne Stroustrup s page   If you so choose  you can still shoot yourself in the foot by inheriting constructors in a derived class in which you define new member variables needing initialization   struct B1       B1 int          struct D1   B1       using B1  B1     implicitly declares D1 int      int x      void test         D1 d 6         Oops  d x is not initialized     D1 e           error  D1 has no default constructor

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You have to explicitly define the constructor in B and explicitly call the constructor for the parent   B int x    A x        or   B     A 5

User · Answer

Constructors are not inherited  They are called implicitly or explicitly by the child constructor   The compiler creates a default constructor  one with no arguments  and a default copy constructor  one with an argument which is a reference to the same type   But if you want a constructor that will accept an int  you have to define it explicitly   class A   public       explicit A int x         class B  public A   public      explicit B int x    A x           UPDATE  In C  11  constructors can be inherited  See Suma s answer for details

User · Answer

Constructors are not inherited  They are called implicitly or explicitly by the child constructor   The compiler creates a default constructor  one with no arguments  and a default copy constructor  one with an argument which is a reference to the same type   But if you want a constructor that will accept an int  you have to define it explicitly   class A   public       explicit A int x         class B  public A   public      explicit B int x    A x           UPDATE  In C  11  constructors can be inherited  See Suma s answer for details

User · Answer

Correct Code is  class A       public         explicit A int x         class B  public A         public        B int a  A a                   main         B  b   new B 5        delete b      Error is b c Class B has not parameter constructor and second it should have base class initializer to call the constructor of Base Class parameter constructor

User · Answer

Correct Code is  class A       public         explicit A int x         class B  public A         public        B int a  A a                   main         B  b   new B 5        delete b      Error is b c Class B has not parameter constructor and second it should have base class initializer to call the constructor of Base Class parameter constructor

User · Answer

Constructors are not inherited  They are called implicitly or explicitly by the child constructor   The compiler creates a default constructor  one with no arguments  and a default copy constructor  one with an argument which is a reference to the same type   But if you want a constructor that will accept an int  you have to define it explicitly   class A   public       explicit A int x         class B  public A   public      explicit B int x    A x           UPDATE  In C  11  constructors can be inherited  See Suma s answer for details

User · Answer

If your compiler supports C  11 standard  there is a constructor inheritance using using  pun intended   For more see Wikipedia C  11 article  You write   class A       public           explicit A int x         class B  public A        using A  A       This is all or nothing - you cannot inherit only some constructors  if you write this  you inherit all of them  To inherit only selected ones you need to write the individual constructors manually and call the base constructor as needed from them   Historically constructors could not be inherited in the C  03 standard  You needed to inherit them manually one by one by calling base implementation on your own

User · Answer

You have to explicitly define the constructor in B and explicitly call the constructor for the parent   B int x    A x        or   B     A 5

User · Answer

You have to explicitly define the constructor in B and explicitly call the constructor for the parent   B int x    A x        or   B     A 5

User · Answer

How about using a template function to bind all constructors   template  lt class    T gt  Derived T    t    Base t

User · Answer

If your compiler supports C  11 standard  there is a constructor inheritance using using  pun intended   For more see Wikipedia C  11 article  You write   class A       public           explicit A int x         class B  public A        using A  A       This is all or nothing - you cannot inherit only some constructors  if you write this  you inherit all of them  To inherit only selected ones you need to write the individual constructors manually and call the base constructor as needed from them   Historically constructors could not be inherited in the C  03 standard  You needed to inherit them manually one by one by calling base implementation on your own

User · Answer

Constructors are not inherited  They are called implicitly or explicitly by the child constructor   The compiler creates a default constructor  one with no arguments  and a default copy constructor  one with an argument which is a reference to the same type   But if you want a constructor that will accept an int  you have to define it explicitly   class A   public       explicit A int x         class B  public A   public      explicit B int x    A x           UPDATE  In C  11  constructors can be inherited  See Suma s answer for details

User · Answer

If your compiler supports C  11 standard  there is a constructor inheritance using using  pun intended   For more see Wikipedia C  11 article  You write   class A       public           explicit A int x         class B  public A        using A  A       This is all or nothing - you cannot inherit only some constructors  if you write this  you inherit all of them  To inherit only selected ones you need to write the individual constructors manually and call the base constructor as needed from them   Historically constructors could not be inherited in the C  03 standard  You needed to inherit them manually one by one by calling base implementation on your own

User · Answer

You have to explicitly define the constructor in B and explicitly call the constructor for the parent   B int x    A x        or   B     A 5

[c++] Inheriting constructors

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