第二章 类与对象基础

学习内容

• 掌握类的定义
• 掌握对象的定义和方法调用
• 熟悉构造函数和析构函数的定义和执行过程
• 掌握复制构造函数和初始化列表的使用

实习任务

• 实习任务一

注意全局对象的生命周期

#include <iostream> 
using namespace std; 
class TestClass{ 
public:
    TestClass(int a){ 
        aa=a;
        cout<<aa<<" Constructed!\n"; 
    }
    ~TestClass(){
        cout<<aa<<" Destructed!\n";
    } 
private:
    int aa; 
};
TestClass AA(3); 
int main(){
//全局对象
    cout<<"In MainFuction."<<endl; 
    TestClass BB(5);
    return 0;
}

运行结果:
3 Constructed!
In MainFuction.
5 Constructed!
5 Destructed!
3 Destructed!
[Finished in 0.3s]

#include <iostream> 
using namespace std; 
class TestClass{ 
public:
    TestClass(){ 
        cout<<" Constructed!\n"; 
    }
    ~TestClass(){
        cout<<" Destructed!\n";
    } 
};
int main(){
    TestClass t1;
    TestClass *p; 
    p=new TestClass; 
    delete p;
    
    return 0;
}

运行结果：
 Constructed!
 Constructed!
 Destructed!
 Destructed!
[Finished in 0.3s]

#include <iostream> 
using namespace std; 
class TestClass{ 
public:
    TestClass(){ 
        cout<<" Constructed!\n"; 
        value = 10;
    }
    ~TestClass(){
        cout<<" Destructed!\n";
    } 
    void setValue(int newValue){
        value = newValue;
    }
    int getValue()const{
        return value;
    }
private:
    int  value;
};
int main(){
    TestClass t1; 
    cout<<t1.getValue()<<endl; 
    TestClass &rt1 = t1; 
    rt1.setValue(20); 
    cout<<t1.getValue()<<endl; 
    TestClass *pt=&t1; 
    pt->setValue(30); //a->b means (*a).b 
    // (*pt).setValue(30);//try uncomment this one
    cout<<t1.getValue()<<endl; 
    return 0;
}

运行结果：
 Constructed!
10
20
30
 Destructed!
[Finished in 0.3s]

#include <iostream>
#include <vector>
using namespace std;
class Test{
public:
    Test():a(1){
        cout<<a<<endl;
    }
    Test(int a){
        cout<<this->a<<endl;
        this->a=a;
        cout<<this->a<<endl;
    }
private:
    int a=3;
};
int main(){
    Test t1;
    Test t2(10);
    return 0;
}

运行结果：
1
3
10
[Finished in 0.4s]

• 实习任务二

要求：编写 Complex 类，封装复数的基本功能

#include <iostream>
#include <cmath>
using namespace std;
class Complex{
public:
    Complex(){
        real = 0;
        image = 0;
    }
    Complex(double n){
        real = n;
        image = 0;
    }
    Complex(double n, double d){
        real = n;
        image = d;
    }
    void setValue(double n, double d){
        real = n;
        image = d;
    }
    double getReal(){
        return real;
    }
    double getImage(){
        return image;
    }
    double getDistance(){
        return sqrt(pow(real,2)-pow(image,2));
    }
    void output(){
        if(image == 0 && real != 0){
            cout<<real<<endl;
        }
        else if(image !=0 && real ==0){
            cout<<image<<'i'<<endl;
        }
        else if(image == 0 && real == 0){
            cout<<0<<endl;
        }
        else{
            if(image<0){
                cout<<real<<image<<'i'<<endl;
            }
            else{
                cout<<real<<'+'<<image<<'i'<<endl;
            }
        }
    }
private:
    double real;
    double image;
};
int main(){
    Complex c1, c2(2), c3(3,4);
    c1.output();
    c2.output();
    c3.output();
    c1.setValue(6,4);
    c1.output();
    cout<<c1.getDistance()<<endl;

    return 0;
}

运行结果：
0
2
3+4i
6+4i
4.47214
[Finished in 0.3s]

• 实习任务三

要求：编写 Time 类，封装对时间的操作，Time 类处理 1 天内的时间，精确到分钟。

#include <iostream>
using namespace std;
class Time{
public:
    Time(){
        hour = 0;
        minute = 0;
    }
    Time(int h, int m){
        hour = h;
        minute = m;
    }
    void setTime(int h, int m){
        hour = h;
        minute = m;
    }
    void output(){
        this->normalizeTime();
        cout<<hour<<':'<<minute<<endl;
    }
    int getHour(){
        return hour;
    }
    int getMinute(){
        return minute;
    }
    int getTotalMinutes(){
        return hour*60 + minute;
    }
private:
    int hour;
    int minute;
    void normalizeTime(){
        hour = ((60*hour + minute)/60)%24;
        minute = minute%60;
    }
};
int main(){
    Time t1(12, 75);
    t1.output();
    t1.setTime(8, 65);
    t1.output();
    cout<<"t1 Hour:"<<t1.getHour()<<endl;
    cout<<"t1 Minute:"<<t1.getMinute()<<endl;
    cout<<"t1 getTotalMinutes:"<<t1.getTotalMinutes()<<endl;

    return 0;
}

运行结果：
13:15
9:5
t1 Hour:9
t1 Minute:5
t1 getTotalMinutes:545
[Finished in 0.3s]

• 实习任务四？

要求：编写随机数类。请实现所要求的成员函数。

#include <iostream>
#include <ctime>
using namespace std;
class RandomNum{
public:
    RandomNum(unsigned int seed){
        if(seed == 0){
            srand((unsigned int)time(NULL));
        }
        else{
            srand(seed);
        }
    }
    void setSeed(unsigned int seed){
        this->seed = seed;
    }
    int random(){
        return rand();
    }
    int random(int max){
        return rand()%max;
    }
    double frandom(){
        return rand()/(double)RAND_MAX;
    }
private:
    unsigned int seed;
};
int main()
{
    RandomNum randomGenerator(100);
    int i;
    for(int i=0; i<10; ++i){
        cout<<randomGenerator.frandom()<<' ';
    }
    cout<<endl;

    return 0;
}

运行结果：
0.000782637 0.153779 0.560532 0.865013 0.276724 0.895919 0.704462 0.886472 0.929641 0.46929 
[Finished in 0.3s]

具体的有关c++随机数的内容可以看这里