How do I call the base class constructor

Question

latley I spent much programming in Java  There you call the class you Inherited from with super     you all probably know that   Now I have a class in C   which has a default constructor which takes some arguments  Example   class BaseClass   public      BaseClass char  name           If I inherit the class it gives me the warning  that there is no appropriate default constructor available  So is there something like super   in C    or do I have to define a function where I initialize all variables

User · Accepted Answer

You do this in the initializer-list of the constructor of the subclass.

class Foo : public BaseClass {
public:
    Foo() : BaseClass("asdf") {}
};

Base-class constructors that take arguments have to be called there before any members are initialized.

User · Answer

In the header file define a base class   class BaseClass   public      BaseClass params        Then define a derived class as inheriting the BaseClass   class DerivedClass   public BaseClass   public      DerivedClass params        In the source file define the BaseClass constructor   BaseClass  BaseClass params           Perform BaseClass initialization     By default the derived constructor only calls the default base constructor with no parameters  so in this example  the base class constructor is NOT called automatically when the derived constructor is called  but it can be achieved simply by adding the base class constructor syntax after a colon      Define a derived constructor that automatically calls its base constructor   DerivedClass  DerivedClass params    BaseClass params           This occurs AFTER BaseClass params  is called first and can        perform additional initialization for the derived class     The BaseClass constructor is called BEFORE the DerivedClass constructor  and the same different parameters params may be forwarded to the base class if desired  This can be nested for deeper derived classes  The derived constructor must call EXACTLY ONE base constructor  The destructors are AUTOMATICALLY called in the REVERSE order that the constructors were called   EDIT  There is an exception to this rule if you are inheriting from any virtual classes  typically to achieve multiple inheritance or diamond inheritance  Then you MUST explicitly call the base constructors of all virtual base classes and pass the parameters explicitly  otherwise it will only call their default constructors without any parameters  See  virtual inheritance - skipping constructors

User · Answer

Regarding the alternative to super  you d in most cases use use the base class either in the initialization list of the derived class  or using the Base  someData syntax when you are doing work elsewhere and the derived class redefines data members   struct Base       Base char  name          virtual  Base        int d      struct Derived   Base       Derived     Base  someString           int d      void foo     d   Base  d

User · Answer

You have to use initiailzers   class DerivedClass   public BaseClass   public    DerivedClass         BaseClass  lt insert arguments here gt                This is also how you construct members of your class that don t have constructors  or that you want to initialize   Any members not mentioned will be default initialized  For example   class DerivedClass   public BaseClass   public    DerivedClass         BaseClass  lt insert arguments here gt         nc  lt insert arguments here gt         di will be default initialized           private    NeedsConstructor nc    CanBeDefaultInit di       The order the members are specified in is irrelevant  though the constructors must come first   but the order that they will be constructed in is in declaration order  So nc will always be constructed before di

User · Answer

There is no super   in C    You have to call the Base Constructor explicitly by name

User · Answer

Use the name of the base class in an initializer-list  The initializer-list appears after the constructor signature before the method body and can be used to initialize base classes and members   class Base   public    Base char  name                          class Derived   Base   public    Derived         Base  hello                             Or  a pattern used by some people is to define  super  or  base  yourself  Perhaps some of the people who favour this technique are Java developers who are moving to C     class Derived   Base   public    typedef Base super    Derived         super  hello

[c++] How do I call the base class constructor?

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