C++第三篇--程序结构

C++第三篇--程序结构

1. 初识程序结构

将类中的成员函数全部放在类外实现，类中只负责声明该函数

person.cpp

#include <stdio.h>

class Person{
private:
    char *name;
    int  age;
    char *work;

public:
    void setName(char *name);

    int setAge(int age);

    void setWork(char *work);

    void printInfo(void);

};

void Person::setName(char *name)
{
    this->name = name;
}

int Person::setAge(int age)
{
        if(age<0 || age>200){
            this->age = 0;
            //return -1;
        }
        else
        {
            this->age = age;
        }

        return age;
}

void Person::setWork(char *work)
{
        this->work = work;
}

void Person::printInfo(void)
{
        printf("name is %s,age is %d,work is %s\n",name,age,work);
}

int main(int argc,char **arcv)
{
    Person per;

    per.setName("LKQ");
    per.setAge(20);
    per.setWork("Student");

    per.printInfo();

    return 0;
}

2. 改进上文程序结构

主要分为两个层次，一个类，一个主函数

• 实现Person类

  • Person.h:提供函数接口
  • Person.c:实现函数

• 实现主函数

person.h

#include <stdio.h>
class Person{
private:
    char *name;
    char age;
    char *work;

public:
    void setName(char *name);

    int setAge(int age);

    void setWork(char *work);

    void printInfo(void);

};

person.cpp

#include <stdio.h>
#include "person.h"

void Person::setName(char *name)
{
        this->name = name;
}

int Person::setAge(int age)
{
        if(age<0 || age>200){
            this->age = 0;
            //return -1;
        }
        else
        {
            this->age = age;
        }

        return age;
}
void Person::setWork(char *work)
{
        this->work = work;
}

void Person::printInfo(void)
{
        printf("name is %s,age is %d,work is %s\n",name,age,work);
}

main.cpp

#include <stdio.h>
#include "person.h"

int main(int argc,char **arcv)
{
    Person per;

    per.setName("LKQ");
    per.setAge(20);
    per.setWork("student");

    per.printInfo();

    return 0;
}

Makefile

person: main.o person.o
    g++ -o $@ $^

%.o : %.cpp
    g++ -c -o $@ $<

clean:
    rm -f *.o person

3. 添加一个Dog类

3.1 引入命名空间：为了解决多个人参加一个工程时，函数命名相同，调用同名函数时候声明属于哪个命名空间就可以解决。

dog.h

namespace c{
    class Dog{
    private:
        char *name;
        int age;
        char *work;

    public:
        void setName(char *name);
        int setAge(int age);
        void printInfo();
    };

    void PersonVersion(void);
}

dog.cpp

#include <stdio.h>
#include "dog.h"

namespace c{
    void Dog::setName(char *name)
    {
        this->name = name;
    }

    int Dog::setAge(int age)
    {
        if(age<0 || age>20)
        {
            this->age = 0;
            //return -1;
        }
        else
        {
            this->age = age;
        }

        return age;
    }

    void Dog::printInfo(){printf("name is %s,age is %d,work is %s\n",name,age,work);}

    void PersonVersion(void)
    {
        printf("Dog V1 by linkaiqiang");
    }
}

person.h

#include <stdio.h>

namespace A{
    class Person{
    private:
        char *name;
        char age;
        char *work;

    public:
        void setName(char *name);

        int setAge(int age);

        void setWork(char *work);

        void printInfo(void);

    };
    void PersonVersion(void);
}

person.cpp

#include <stdio.h>
#include "person.h"

namespace A{
    void Person::setName(char *name)
    {
        this->name = name;
    }

    int Person::setAge(int age)
    {
        if(age<0 || age>200){
            this->age = 0;
            //return -1;
        }
        else
        {
            this->age = age;
        }

        return age;
    }

    void Person::setWork(char *work)
    {
        this->work = work;
    }

    void Person::printInfo(void)
    {
        printf("name is %s,age is %d,work is %s\n",name,age,work);
    }

    void PersonVersion(void){
        printf("Person V1 by linkaiqiang");
    }
}

main.cpp

#include <stdio.h>
#include "person.h"
#include "dog.h"

int main(int argc,char **argv)
{
    A::Person per;

    per.setName("zhangsan");
    per.setAge(20);
    per.setWork("Student");
    per.printInfo();

    c::Dog dog;

    dog.setName("xiaozhao");
    dog.setAge(1);
    dog.printInfo();

    A::PersonVersion();
    printf("\n");

    c::PersonVersion();
    printf("\n");
    return 0;
}

Makefile

person: main.o person.o dog.o
    g++ -o $@ $^

%.o : %.cpp
    g++ -c -o $@ $<

clean:
    rm -f *.o person

3.2 直接使用类

修改main.cpp

#include <stdio.h>
#include "person.h"
#include "dog.h"

//global namespace
/*将A::person放入全局变量，以后可以用Person来表示A::person，下面同理*/
using A::Person;
using c::Dog;

/*
using A::PersonVersion;
using c::PersonVersion;
*/
//会发生冲突，如果是两个命名空间当中相同函数定义为全局

int main(int argc,int **arcv)
{

    //local namespace
    Person per;

    per.setName("zhangsan");
    per.setAge(20);
    per.setWork("Student");
    per.printInfo();

    Dog dog;

    dog.setName("xiaozhao");
    dog.setAge(1);
    dog.printInfo();

    A::PersonVersion();
    printf("\n");

    c::PersonVersion();
    printf("\n");
    return 0;
}

3.3使用namespace导入所有类和函数

修改main.cpp

#include <stdio.h>
#include "person.h"
#include "dog.h"

using namespace A;
using namespace c;

//将所有函数，所有类导入

int main(int argc,int **arcv)
{

    //local namespace
    Person per;

    per.setName("zhangsan");
    per.setAge(21);
    per.setWork("student");
    per.printInfo();

    Dog dog;

    dog.setName("xiaozhao");
    dog.setAge(1);
    dog.printInfo();

    A::PersonVersion();
    printf("\n");
    c::PersonVersion();
    printf("\n");
    return 0;
}

4. 引入iostream

之前的程序都是用printf实现打印函数，现在C++标准输出输入流实现

dog.h

namespace C {
class Dog{
private:
    char *name;
    int  age;

public:
    void setName(char *name);
    int setAge(int age);
    void printInfo();
};

void printVersion(void);
}

dog.cpp

#include <iostream>
#include "dog.h"
#include <stdio.h>

using namespace std;

namespace C {
    void Dog::setName(char *name)
    {
        this->name = name;
    }

    int Dog::setAge(int age)
    {
        if(age<0 || age>20){
            this->age = 0;
            return -1;
        }
        else
        {
            this->age = age;
        }

        return 0;
    }

    void Dog::printInfo()
    {
    cout<<"name is "<<name<<" age is "<<age<<endl;
    }

    void printVersion(void)
    {
        cout<<"Dog V1 by linkaiqiang"<<endl;;
    }
}

person.h

#include <stdio.h>

namespace A {
    class Person{
    private:
        char *name;
        int  age;
        char *work;

    public:
        void setName(char *name);

        int setAge(int age);

        void setWork(char *work);

        void printInfo(void);

    };
    void printVersion(void);
}

person.cpp

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

namespace A {

    void Person::setName(char *name)
    {
        this->name = name;
    }

    int Person::setAge(int age)
    {
        if (age < 0 || age > 150)
        {
            this->age = 0;
            return -1;
        }
        this->age = age;
        return 0;
    }

    void Person::setWork(char *work)
    {
        this->work = work;
    }

    void Person::printInfo(void)
    {
        std::cout<<"name = "<<name<<" age = "<<age<<" work = "<<work<<std::endl;
    }

    void printVersion(void)
    {
        std::cout<<"Person v1, by weidongshan"<<std::endl;
    }

}

main.cpp

#include "person.h"
#include "dog.h"
#include <stdio.h>

using namespace A;
using namespace C;

//将所有函数，所有类导入

int main(int argc,int **argv)
{

    //local namespace
    Person per;

    per.setName("zhangsan");
    per.setAge(20);
    per.setWork("student");
    per.printInfo();

    Dog dog;

    dog.setName("xiaozhao");
    dog.setAge(1);
    dog.printInfo();

    A::printVersion();
    printf("\n");
    C::printVersion();
    printf("\n");
    return 0;
}

Makefile

person: main.o person.o dog.o
g++ -o $@ $^

%.o : %.cpp
g++ -c -o $@ $<

clean:
rm -f *.o person

5. 总结

• 类定义(.h)/类实现(.cpp)
  • .h/.cpp文件中：

namespace a
//声明或定义函数;
int fun();
void fun2()...

• 命名空间
  • 直接使用: a::fun, a::fun2
  • using声明:using a::fun; // 以后调用fun即表示a::fun
  • using编译:using namespace a ; // 以后调用fun, fun2即可