默认参数的构造函数与虚函数及常量初始化

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于 2014-11-22 22:56:33 发布

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分类专栏： ACM_C++系列

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本文详细介绍了C++中类的构造函数如何初始化成员变量，通过实例展示了成员变量之间的依赖关系和构造过程。

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#include <iostream>
using namespace std;

class myclass {
    int a, b;
public:
    myclass(int i = 0, int j = 0);
    void show();
};
myclass::myclass(int i, int j) {
    a = i;
    b = j;
    cout << "constructor called" << endl;
}
void myclass::show() {
    a += b;
    b += a;
    cout << "a = " << a << " " << "b = " << b << endl;
}
int main() {
    myclass ob1;
    ob1.show();
    myclass ob2(6);
    ob2.show();
    myclass ob3(2, 8);
    ob3.show();
    return 0;
}

#include <iostream>
using namespace std;

class A {
public:
    virtual~A() {
        cout << "A::~A() called.\n";
    }
};
class B:public A {
public:
    B(int i) {
        buf = new char[i];
    }
    virtual ~B(){
        delete []buf;
        cout << "B::~B called.\n";
    }
private:
    char *buf;
};
void fun(A *a) {
    delete a;
}
int main() {
    A *a = new B(15);
    fun(a);
}

#include <iostream>
using namespace std;

class A {
public:
    A(int i);
    void print();
    const int& r;
private:
    const int a;
    static const int b;
};
const int A::b = 10;
A::A(int i):a(i), r(a){}
void A::print() {
    cout << a << ":"  << b << ":"<< r << endl;
}
int main() {
    A a1(100), a2(0);
    a1.print();
    a2.print();
}