Inheritance :Getting back to the basics

This is a discussion on Inheritance :Getting back to the basics within the C++ Programming forums, part of the General Programming Boards category; Hi, please help Code: #include <iostream> class Base { public: Base ( int d ) {data = d;} void Show() ...

  1. #1
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    Inheritance :Getting back to the basics

    Hi, please help

    Code:
    #include <iostream> 
    
    class Base {
    
    public:
    	Base ( int d ) {data = d;}
    	void Show() { std::cout << "I'm showig off " << data << " in base"; }
    private :
    	int data;
    };
    
    class Derived : public Base {
    
    public:
    	Derived() {}
    	void Showd() {
    		Show();
    	}
    };
    
    void main () {
    	Base b(5);
    	Derived	d;
    	d.Show();
    }
    : error C2512: 'Base' : no appropriate default constructor available ?????

  2. #2
    C++ Witch laserlight's Avatar
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    Yes, since Base has a user declared constructor, the compiler will not provide it a default constructor. Now, the Derived class default constructor implicitly invokes Base's default constructor, hence the error. You can either explicitly initialise Base in the Derived default constructor's initialisation list, or you can provide Base with a default constructor.
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    Quote Originally Posted by laserlight View Post
    Yes, since Base has a user declared constructor, the compiler will not provide it a default constructor. Now, the Derived class default constructor implicitly invokes Base's default constructor, hence the error. You can either explicitly initialise Base in the Derived default constructor's initialisation list, or you can provide Base with a default constructor.
    like this

    Code:
    Derived() : Base() {}

  4. #4
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    Quote Originally Posted by csonx_p View Post
    like this

    Code:
    Derived() : Base() {}
    k ...

    Code:
    Derived::Derived() : Base (5) {
    }

  5. #5
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    Abstract class

    Code:
    #include <iostream> 
    
    class Base {
    
    public:
    	Base ( int d ) { data = d;}
    	void setData( int d ) { data = d;} 
    	virtual void Show() = 0;
    protected :
    	int data;
    };
    
    class Derived : private Base {
    
    public:
    	Derived();
    	void setData( int d ) { data = d; }
    	void Show() { std::cout << "I'm showig off " << data << " in base"; }
    };
    
    Derived::Derived() : Base (5) {
    }
    
    void main () 
    {
    	Derived	d;	
    	Base * b = &d;
    
    	b->Show();
    	d.setData(10);
    	std::cout << "\n";
    	b->Show();
    }
    error C2243: 'type cast' : conversion from 'Derived *__w64 ' to 'Base *' exists, but is inaccessible ???

    thnx

  6. #6
    C++ Witch laserlight's Avatar
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    You are using private inheritance.
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  7. #7
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    Quote Originally Posted by laserlight View Post
    You are using private inheritance.
    lol, forgot to remove tht... But gave me more knowledge .. thanx

  8. #8
    C++まいる!Cをこわせ! Elysia's Avatar
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    You are using void main. Why?
    Quote Originally Posted by Adak View Post
    io.h certainly IS included in some modern compilers. It is no longer part of the standard for C, but it is nevertheless, included in the very latest Pelles C versions.
    Quote Originally Posted by Salem View Post
    You mean it's included as a crutch to help ancient programmers limp along without them having to relearn too much.

    Outside of your DOS world, your header file is meaningless.

  9. #9
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    Quote Originally Posted by Elysia View Post
    You are using void main. Why?
    just for testing purposes? But now that you've asked, why not?

  10. #10
    C++ Witch laserlight's Avatar
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    Quote Originally Posted by csonx_p
    just for testing purposes? But now that you've asked, why not?
    Because it is non-standard, and you have nothing to gain since changing void to int is enough.
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  11. #11
    C++まいる!Cをこわせ! Elysia's Avatar
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    Quote Originally Posted by csonx_p View Post
    just for testing purposes? But now that you've asked, why not?
    As a member of this board, you should be fully aware that void main is frowned upon here (just see Salem's avatar).
    Quote Originally Posted by Adak View Post
    io.h certainly IS included in some modern compilers. It is no longer part of the standard for C, but it is nevertheless, included in the very latest Pelles C versions.
    Quote Originally Posted by Salem View Post
    You mean it's included as a crutch to help ancient programmers limp along without them having to relearn too much.

    Outside of your DOS world, your header file is meaningless.

  12. #12
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    Quote Originally Posted by Elysia View Post
    just see Salem's avatar.
    ...

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