C ++ 中类赋初值的方法

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作者在 2010-07-02 20:11:37 发布以下内容

#include "dd.h"
#include <iostream.h>

class A {
private:
 const int x;
 enum { num =10};
 static int y,z;
 int arr[num];
public:
 A (int val = 0):x(val)
 {
 for (int i=0;i<x;i++)
 {
 arr[i] = i;
 }
 cout<<"static value1 A::y = "<<y<<endl;
 y = 0;
 cout<<"static value2 A::y = "<<y<<endl;
 }
 ~A(){cout<<"destructor..."<<endl;}
 void printf();
};

void A::printf()
{
 y = 121;
 cout<<"const value A::x = "<<x<<endl;
 cout<<"static value A::y = "<<y<<endl;
 cout<<"static value A::z = "<<z<<endl;
 for (int i=0;i<num;i++)
 cout<<arr[i]<<"\t"<<endl;
}

int A::y =120;
int A::z =130;

int main()
{
 A a(5) ;
 a.printf();

 A b(4) ;
 b.printf();

 i = 12;
 return 0;
}

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文章评论，共5条

vfdff(作者)

2010-07-02 22:31

#include <stdio.h> 
#include <iostream.h> 
 
class A { 
private: 
 
//public: 
   int size; 
   int first,last; 
 
public: 
    A (int f = 0,int l=0):first(f),last(l),size(f-l) { 
        last = l; 
        size = first-last; 
         cout<<"first="<<first<<"\t"<<"last="<<last<<"\t"<<"size="<<size<<endl; 
        cout<<"constructor A..."<<endl; 
    } 
    ~A(){cout<<"destructor A..."<<endl;} 
    inline void printf(); 
}; 
 
class B : public  A { 
    int temp; 
public: 
    B ( int t=0 ,int f=0,int l=0) : temp(t),A(temp,l) 
    { 
          A (temp,l); 
//         temp = t; 
        //cout<<"first="<<first<<"\t"<<"last="<<last<<"\t"<<"size="<<size<<"\t"<<"temp="<<temp<<endl; 
        cout<<"constructor B..."<<endl; 
    } 
    ~B(){cout<<"destructor B..."<<endl;} 
    void printf(); 
}; 
 
inline void A::printf() 
{ 
    cout<<"first="<<first<<"\t"<<"last="<<last<<"\t"<<"size="<<size<<endl; 
} 
 
void B::printf() 
{ 
    cout<<"temp="<<temp<<"\t"; 
    A::printf(); 
} 
 
int main() 
{ 
    A a(10,20) ; 
    a.printf(); 
 
    B b(3,9,27) ; 
    b.printf(); 
 
    cout<<"sizeof(A)="<<sizeof(A)<<"\t"<<"sizeof(B)="<<sizeof(B)<<endl; 
    return 0; 
}

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vfdff(作者)

2010-07-02 22:36

#include <stdio.h> 
#include <iostream.h> 
 
class Base { 
private: 
public: 
   int x; 
public: 
    Base (int initialValue=0):x(initialValue) { } 
    Base& operator= (const Base& ); 
    void printf(); 
    void f(int x){}; 
}; 
 
class Derived : public  Base { 
    int y; 
public: 
    Derived (int initialValue=0,int b=0):Base(initialValue),y(b) { }; 
    Derived& operator = (const Derived&  ); 
    void printf(); 
    void f(char* str){}; 
}; 
 
 
 
Base& Base::operator= (const Base& rhs) 
{ 
    if (this==&rhs) 
        return *this; 
    
    x = rhs.x; 
    return *this; 
} 
 
Derived& Derived::operator = (const Derived& rhs) 
{ 
    if (this==&rhs) 
        return *this; 
    
    Base::operator = (rhs) ;  // 调用 this->Base::operator=(rhs) 
    //x = rhs.x; 
    y = rhs.y; 
    return *this; 
} 
 
void Base::printf() 
{ 
    cout<<"x="<<x<<endl; 
} 
 
void Derived::printf() 
{ 
    cout<<"y="<<y<<"\t"; 
    Base::printf(); 
} 
 
 
void putout(int x){} 
void putout(float x){} 
void putout(double x){} 
 
int main() 
{ 
    Derived d0(0,2) ; 
    d0.printf(); 
    Derived d1(1,3) ; 
    d1.printf(); 
 
 
    d0 = d1; 
    d0.printf(); 
 
    Base *pd = new Derived; 
    pd->f(10); 
 
    putout(0.1); 
    return 0; 
}

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vfdff(作者)

2010-07-02 22:45

#include <stdio.h> 
#include <iostream.h> 
 
class Base { 
private: 
public: 
   int i; 
public: 
    Base (int initialValue=0):i(initialValue) { } 
    virtual int sum() const { 
        cout<<"base"<<endl; 
        return i; 
    } 
    void printf(); 
    void f(int x){}; 
}; 
 
class Derived : public  Base { 
    int j; 
public: 
    Derived (int initialValue=0,int b=0):Base(initialValue),j(b) { }; 
    int sum() const { 
        cout<<"Derived"<<endl; 
        return Base::sum()+j; 
    } 
 
    void printf(); 
    void f(char* str){}; 
}; 
 
void call(Base b) 
{ 
    cout<<"sum="<<b.sum() <<endl; 
} 
 
void tune(Base* b) 
{ 
    cout<<"sum="<<b->sum() <<endl; 
} 
void Base::printf() 
{ 
    cout<<"i="<<i<<endl; 
} 
 
void Derived::printf() 
{ 
    cout<<"j="<<j<<"\t"; 
    Base::printf(); 
} 
 
 
int main() 
{ 
    Base b(10); 
    Derived d(10,47); 
    call(b); 
    call(d); 
 
    tune(&b); 
    tune(&d); 
 
    return 0; 
}

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vfdff(作者)

2010-07-02 22:46

#include <iostream> 
using namespace std; 
 
 
const int i =99; 
class Z { 
 
private: 
    int aa; 
    int ii ;   
    
protected: 
    int aaa; 
    int iii  ;   
public: 
    //enum { i = 7 }; 
    int a; 
    int f()   
    { 
        ii = 3; 
        //i0 = 4; 
        return i; 
    } 
    enum { i = 7 }; 
     //static  int i0 ; 
}; 
 
Z z; 
 
int main() 
{ 
//       z.i0 = 3; 
//      Z :: i0 = 4; 
    cout << z.f() <<endl; 
//   cout <<  z.i <<" " <<sizeof(z.a)<<endl; 
    return 0; 
}

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vfdff(作者)

2010-08-08 00:33

//    2006.7.25 
 
#include <stdio.h> 
 
 
class A { 
    public : 
    virtual void printOn(){}   //  纯虚函数，实现多态性 
}; 
 
class B : public A { //定义一个类 B，为类  A 的公共继承 
    public: 
    virtual void printOn() {puts("\nClass B");} 
}; 
 
class C : public B { 
    public: 
    virtual void printOn() {puts("\nClass C");} 
}; 
 
void Show(A *a) 
{ 
    a->printOn(); 
} 
 
void main() 
{ 
    B *b = new B; 
    Show(b);     // B::printOn() 
    C *c = new C; 
    Show(c);     // C::printOn() 
    delete b; 
    delete c; 
 
 
        b = new C; 
    Show(b);     // C::printOn() 
    c = (C *) new B; 
    Show(c);     // B::printOn() 
    delete b; 
        delete c; 
}

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