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Is it true that by base class pointer you can call only those functions of derived class which are inherited from the base class?
Wiki User
∙ 11y ago
Yes, provided those functions are declared virtual. If they are not virtual, the base class method is implicitly called instead. The base class should be thought of as a common interface to the objects that derive from it, while the derived objects are "more specialised" forms of the base class, which can override the virtual base class methods to produce more specific behaviour. The less derived the object, the less specialised it becomes.
Certain functions can be predicted for all derived objects, but cannot be implemented in the base class. For instance, all shapes can be drawn, but a shape base class cannot implement a Draw() function unless it knows what type of shape it actually is. But by deriving specific shapes such as circles and squares from the shape class, they can each provide their own implementations for the Draw() function, which can then be declared pure-virtual in the base class. This not only ensures that every derived shape provides its own Draw() method, but also ensures that no instances of shape can be created other than by derived objects. The shape then becomes abstract; so shape is a conceptual object while circles and squares are actual objects.
Wiki User
∙ 11y ago
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Which base class member functions are not inherited by a derived class?
Derived classes only inherit the protected and public members of their base classes. Private member functions cannot be inherited by a derived class.
How does virtual function support run time polymorphism?
Virtual functions are used to suport runtime polymorphism.In C++,if we have inheritance and we have overridden functions in the inherited classes,we can declare a base class pointer and make it to point to the objects of derived classes.When we give a keyword virtual to the base class functions,the compiler will no do static binding,so during runtime ,the base class pointer can be used to call the functions of the derived classes.Thus virtual functions support dynamic polymorphism.
What is the Practical application of a derived class object stored in base class pointer?
If you have base class derived object pointing by base class pointer, then you have the power of run time polymorphism in your hand, which gives you the ability to call the derived class implementation of the virtual member function. If we declare the member function as virtual in base class which needs to overridden in derived class, then you can decide at run time which implementation will be called at run time.
What are the application of this pointer can you use this pointer in friend function justify?
The this pointer can only be used within nonstatic member functions. Friend functions are not members so they have no access to a this pointer. However, you can pass a specific instance of a class to a function via a class reference argument. To understand how friendship works, first understand that a nonstatic member function has the following properties: 1. It has private access to the class. 2. It is scoped to the class. 3. It must be invoked upon an object of the class (has a this pointer). Static member functions have the first two properties while friend functions only have the first property.
Is it true that a derived class inherits all the members of its base class?
False. A derived class inherits the public and protected members of its base class. Private members of the base class cannot be inherited.
Which base class member functions are not inherited by a derived class?
Derived classes only inherit the protected and public members of their base classes. Private member functions cannot be inherited by a derived class.
How does virtual function support run time polymorphism?
Virtual functions are used to suport runtime polymorphism.In C++,if we have inheritance and we have overridden functions in the inherited classes,we can declare a base class pointer and make it to point to the objects of derived classes.When we give a keyword virtual to the base class functions,the compiler will no do static binding,so during runtime ,the base class pointer can be used to call the functions of the derived classes.Thus virtual functions support dynamic polymorphism.
What is the Practical application of a derived class object stored in base class pointer?
If you have base class derived object pointing by base class pointer, then you have the power of run time polymorphism in your hand, which gives you the ability to call the derived class implementation of the virtual member function. If we declare the member function as virtual in base class which needs to overridden in derived class, then you can decide at run time which implementation will be called at run time.
What are the application of this pointer can you use this pointer in friend function justify?
The this pointer can only be used within nonstatic member functions. Friend functions are not members so they have no access to a this pointer. However, you can pass a specific instance of a class to a function via a class reference argument. To understand how friendship works, first understand that a nonstatic member function has the following properties: 1. It has private access to the class. 2. It is scoped to the class. 3. It must be invoked upon an object of the class (has a this pointer). Static member functions have the first two properties while friend functions only have the first property.
Is it true that a derived class inherits all the members of its base class?
False. A derived class inherits the public and protected members of its base class. Private members of the base class cannot be inherited.
Does Derive class inherits?
The derived class inherits all members and member functions of a base class.
What is base class pointer?
It is exactly what it says it is: a pointer to a base class. The assumption is that you have an object to a derived class, but actually hold a pointer to its base class. The following minimal example demonstrates this: class base{ public: virtual ~base(){} }; class derived: public base{}; int main() { base* p = new derived; // base class pointer to a derived instance. delete( p ); return(0); } Note that derived has an "is-a" relationship with base (derived is a base), thus the above code is perfectly legal. Moreover, because the base class destructor is declared virtual, when you delete p you automatically destroy the instance of derived before the instance of base, thus ensuring a clean teardown (without a virtual destructor, a dangling reference to derived would be left behind, which will only lead to problems further down the line). Taking things further, calling any virtual methods upon the base class automatically invokes the override in your derived class, thus ensuring that your derived class behaves accordingly, polymorphically, even though you only hold a pointer to the base class. In other words, the base class provides a generic interface that is common to all its derivatives, and you can call those generic methods via the base class pointer without ever needing to know the actual derived type. Remember that base classes should never know anything about their derivatives since a new derivative could be created at any time in the future and would therefore be impossible to predict in advance. But so long as the derivative makes use of the virtual functions (the generic interface) provided by the base class, there is never any need to know the actual type. The derivative's own v-table takes care of that for you, thus completely eliminating the need for expensive runtime type information and dynamic downcasts (which is always a sign of poor class design). This then makes it possible for your derived class overrides to call non-generic methods, thus extorting non-generic behaviour from what is essentially a generic, base class pointer.
What do you mean by protected derivation of a sub class from base class?
When you derive a class (the sub-class) from a base class using protected access, all public members of the base class become protected members of the derived class, while protected members of the base class will remain protected. Private members are never inherited so they remain private to the base class. By contrast, if you use public inheritance, the public members of the base class remain public to the derived class, while protected members of the base class remain protected in the derived class. If you use private inheritance, both the public and protected members of the base class become private to the derived class. Note that accessibility cannot be increased, only reduced or left the same. That is, a protected member of a base class cannot be inherited as a public member of a derived class -- it can only be declared private or remain protected. Note also that accessibility is viewed from outside of the derived class. That is, all members of a base class other than the private members are inherited by the derived class and are therefore fully accessible to the derived class. But from outside of the derived class, all base class accessibility is determined by the access specified by the type of inheritance.
How you declare class scoped variables and member functions?
To scope class members to the class (rather than to instances of the class), declare them as static members of the class. Static members are accessible even when no instances of the class exist. As such, static member functions do not have access to a 'this' pointer, unlike ordinary (nonstatic) member functions.
What do you mean by inheriting the interface?
In object oriented programming, a derived class inherits the protected and public members of its base class. Those members therefore define the interface that is inherited by the derived class. The derived class may augment that interface to provide a more specialised implementation of the interface, without the need to re-write the generic interface of the base class. The implication is that the derived class is a more specialised form of the base class.
Why private data members or functions are not inherited?
Because that's what private means. Private data members or functions are intended to be usable only in the base class, and the inheriting class can only access protected or public members or functions.
How can you access private functions of a class from the Main function in Cpp?
Any member functions and data members declared as 'private' in a class, can only be accessed directly by functions within the class.They cannot be accessed directly by derived objects, nor from anywhere outside an object of the class, such as from the Main function.To access private class members, you must rely on what are called accessor functions. Accessor functions are functions inside the class, either public or protected, which automatically have access to private members.If a function from Main, or elsewhere outside the class hierarchy, needs access, then you need to use publicaccessor functions. For derived class access, you can use protected accessor functions.
