學習 c++ 物件導向

---

tags: c++,物件導向,指標,static,class

Wed, Jul 21, 2021 2:31 PM

• 學習 c++ 物件導向 Image Not Showing Possible Reasons The image file may be corruptedThe server hosting the image is unavailableThe image path is incorrectThe image format is not supported Learn More →
  • classes(類別) Image Not Showing Possible Reasons The image file may be corruptedThe server hosting the image is unavailableThe image path is incorrectThe image format is not supported Learn More →
  • constructors & destructors(建構子&解構子) Image Not Showing Possible Reasons The image file may be corruptedThe server hosting the image is unavailableThe image path is incorrectThe image format is not supported Learn More →
  • Overloading Constructors(重載建構子) Image Not Showing Possible Reasons The image file may be corruptedThe server hosting the image is unavailableThe image path is incorrectThe image format is not supported Learn More →
  • Pointers to Classes(類別指標) Image Not Showing Possible Reasons The image file may be corruptedThe server hosting the image is unavailableThe image path is incorrectThe image format is not supported Learn More →
  • Overloading Operators(重載運算子) Image Not Showing Possible Reasons The image file may be corruptedThe server hosting the image is unavailableThe image path is incorrectThe image format is not supported Learn More →
  • This(this指標) Image Not Showing Possible Reasons The image file may be corruptedThe server hosting the image is unavailableThe image path is incorrectThe image format is not supported Learn More →
  • Static Members(靜態成員) Image Not Showing Possible Reasons The image file may be corruptedThe server hosting the image is unavailableThe image path is incorrectThe image format is not supported Learn More →
  • Friend(朋友函式) Image Not Showing Possible Reasons The image file may be corruptedThe server hosting the image is unavailableThe image path is incorrectThe image format is not supported Learn More →
  • Inheritance(繼承) Image Not Showing Possible Reasons The image file may be corruptedThe server hosting the image is unavailableThe image path is incorrectThe image format is not supported Learn More →
  • Pointers to Base Class(父類別指標) Image Not Showing Possible Reasons The image file may be corruptedThe server hosting the image is unavailableThe image path is incorrectThe image format is not supported Learn More →
  • Polymorphism：Virtual Members(虛擬成員) Image Not Showing Possible Reasons The image file may be corruptedThe server hosting the image is unavailableThe image path is incorrectThe image format is not supported Learn More →
  • Polymorphism：Abstract Base Classes(抽象類別) Image Not Showing Possible Reasons The image file may be corruptedThe server hosting the image is unavailableThe image path is incorrectThe image format is not supported Learn More →

歡迎觀賞！！

---

classes(類別)

#include <iostream>


/*
宣告一個名稱為 cat 的類別
-----------------
變數:
    count 數量
    posx 紀錄x位置
    posy 紀錄y位置
-----------------
函數:
    set_pos 設定位置
    get_count 回傳數量
-----------------
*/
class cat{
    public:
        void set_pos(int,int);
        int get_count();
    private:
        int count = 1;
        int posx,posy;
};

void cat::set_pos(int x,int y){
    posx = x;
    posy = y;
}

int cat::get_count(){
    return count;
}

int main ()
{
    cat c1;
    c1.set_pos(1,2);
    std::cout << c1.get_count() << std::endl;
}

練習使用classes，並且了解到public和private的使用方式，以及成員函式的宣告，可以先宣告原型再利用外部宣告。

---

constructors & destructors(建構子&解構子)

#include <iostream>


/*
宣告一個名稱為 cat 的類別
-----------------
變數:
    *count 數量的指標
    *posx 紀錄x位置的指標
    *posy 紀錄y位置的指標
-----------------
函數:
    cat 設定初始值的建構子
    get_count 回傳指標的數量
    ~cat 刪除資料的解構子
-----------------
*/
class cat{
    public:
        cat(int,int,int);
        int get_count();
        ~cat();
    private:
        int *count;
        int *posx,*posy;
};

cat::cat(int x,int y,int cnt){
    posx = new int;
    posy = new int;
    count = new int;
    *posx = x;
    *posy = y;
    *count = cnt;
}

cat::~cat(){
    delete posx;
    delete posy;
    delete count;
}

int cat::get_count(){
    return *count;
}

int main ()
{
    cat c1 (1,2,5);
    std::cout << c1.get_count() << std::endl;
}

練習使用constructors & destructors，了解建構子和解構子的用途，以及使用方法。

！！解構子最常使用的地方在於動態管理的記憶體釋放。

---

Overloading Constructors(重載建構子)

#include <iostream>


/*
宣告一個名稱為 cat 的類別
-----------------
變數:
    count 數量
    posx 紀錄x位置
    posy 紀錄y位置
-----------------
函數:
    get_count 回傳數量
-----------------
*/
class cat{
    public:
        int get_count();
        int count,posx,posy;
};


int cat::get_count(){
    return count;
}

int main ()
{
    cat c1 ({5,2,5}); // [or] cat c1
    
    std::cout << c1.get_count() << std::endl;
}

預設的建構子為 cat()，有兩種，第一種是無初始化空的建構子，第二種是可以初始化的建構子
empty constructor

cat(){}

copy constructor

cat(const &cat rv){
 count = rv.count;
 posx = rv.posx;
 posy = rv.posy;
}

多載函式
cat()
cat(int,int)
可以寫成兩種同樣名稱的函式。

！！取代了預設的函式，所以原本的預設函式已經不存在了

#include <iostream>


/*
宣告一個名稱為 cat 的類別
-----------------
變數:
    *count 數量的指標
    *posx 紀錄x位置的指標
    *posy 紀錄y位置的指標
-----------------
函數:
    cat 設定初始值的建構子
    get_count 回傳指標的數量
    ~cat 刪除資料的解構子
-----------------
*/
class cat{
    public:
        cat();
        cat(int,int,int);
        int get_count();
        int count,posx,posy;
};

cat::cat(){
    count = 1;
    posx = 1;
    posx = 1;
}

cat::cat(int cnt,int x,int y){
    count = cnt;
    posx = x;
    posy = y;
}

int cat::get_count(){
    return count;
}

int main ()
{
    cat c1 (1,2,3);
    cat c2;
    std::cout << c1.get_count() << std::endl;
}

---

Pointers to Classes(類別指標)

#include <iostream>


/*
宣告一個名稱為 cat 的類別
-----------------
變數:
    count 數量
    posx 紀錄x位置
    posy 紀錄y位置
-----------------
函數:
    set_value 設定數值
    get_count 回傳數量
-----------------
*/
class cat{
    public:
        int set_value(int, int, int);
        int get_count();
        int count,posx,posy;
};

int cat::set_value(int a, int b, int c){
    count = a;
    posx = b;
    posy = c;
}

int cat::get_count(){
    return count;
}

int main ()
{
    cat c1;
    cat *c2;
    cat *c3;
    cat *c4;
    c2 = new cat;
    c3 = new cat[2];
    c4 = &c1;
    c1.set_value(1,1,2);
    c2->set_value(2,3,4);
    c3->set_value(3,4,5);
    c3[1].set_value(3,5,6);
    std::cout << "c1 " << c1.get_count() << std::endl;
    std::cout << "c2 " << c2->get_count() << std::endl;
    std::cout << "c3[0] " << c3->get_count() << std::endl;
    std::cout << "c3[1] " << c3[1].get_count() << std::endl;
    std::cout << "c4 " << c4->get_count() << std::endl;
}

練習使用指向class的指標，以及pointer的使用方式。

---

Overloading Operators(重載運算子)

#include <iostream>


/*
宣告一個名稱為 cat 的類別
-----------------
變數:
    count 數量
    posx 紀錄x位置
    posy 紀錄y位置
-----------------
函數:
    set_value 設定數值
    get_count 回傳數量
    operator+ 重載運算值
-----------------
*/
class cat{
    public:
        int count,posx,posy;
        void set_value(int, int, int);
        int get_count();
        cat operator +(cat);
};

void cat::set_value(int a, int b, int c){
    count = a;
    posx = b;
    posy = c;
}

int cat::get_count(){
    return count;
}

cat cat::operator+(cat c){
    cat temp;
    temp.count = count + c.count;
    temp.posx = posx + c.posx;
    temp.posy = posy + c.posy;
    return temp;
}

int main ()
{
    cat c1,c2,c3;
    c1.set_value(1,1,2);
    c2.set_value(2,3,4);
    c3 = c1 + c2;
    std::cout << "c3 " << c3.get_count() << " " << c3.posx << " " << c3.posy << std::endl;
}

---

This(this指標)

#include <iostream>


/*
宣告一個名稱為 cat 的類別
-----------------
變數:
    count 數量
    posx 紀錄x位置
    posy 紀錄y位置
-----------------
函數:
    set_value 設定數值
    get_count 回傳數量
    isitme 檢查是否為正確的物件
    operator+ 重載運算值
-----------------
*/
class cat{
    public:
        int count,posx,posy;
        void set_value(int, int, int);
        int get_count();
        bool isitme(cat& param);
        cat operator +(cat);
};

void cat::set_value(int a, int b, int c){
    count = a;
    posx = b;
    posy = c;
}

int cat::get_count(){
    return count;
}

bool cat::isitme(cat& param){
    if(&param == this) return 1;
    else return 0;
}

cat cat::operator+(cat c){
    
    count = count + c.count;
    posx = posx + c.posx;
    posy = posy + c.posy;
    return *this;
}

int main ()
{
    cat c1,c2,c3;
    c1.set_value(1,1,2);
    c2.set_value(2,3,4);
    c3 = c1 + c2;
    cat* c4;
    c4  = &c3;
    if(c4->isitme(c3))
        std::cout << "c3 " << c4->get_count() << " " << c4->posx << " " << c4->posy << std::endl;
}

---

Static Members(靜態成員)

#include <iostream>


/*
宣告一個名稱為 cat 的類別
-----------------
變數:
    count 數量
    posx 紀錄x位置
    posy 紀錄y位置
-----------------
函數:
    set_value 設定數值
    get_count 回傳數量
    get_allcnt 回傳總數量
    isitme 檢查是否為正確的物件
    operator+ 重載運算值
-----------------
*/
class cat{
    public:
        int count,posx,posy;
        void set_value(int, int, int);
        int get_count();
        static int get_allcnt();
        bool isitme(cat& param);
        cat operator +(cat);
    private:
    static int cnt;
};

void cat::set_value(int a, int b, int c){
    count = a;
    cnt += count;
    posx = b;
    posy = c;
}

int cat::get_count(){
    return count;
}

int cat::get_allcnt(){
    return cnt;
}

bool cat::isitme(cat& param){
    if(&param == this) return 1;
    else return 0;
}

cat cat::operator+(cat c){
    count = count + c.count;
    posx = posx + c.posx;
    posy = posy + c.posy;
    return *this;
}

int cat::cnt = 0;

int main ()
{
    cat c1,c2,c3;
    c1.set_value(1,1,2);
    c2.set_value(2,3,4);
    c3 = c1 + c2;
    cat* c4;
    c4  = &c3;
    if(c4->isitme(c3))
        std::cout << "c3 " << c4->get_count() << " " << c4->posx << " " << c4->posy << std::endl;
    std::cout << "all:" << cat::get_allcnt() << std::endl;
}

---

Friend(朋友函式)

#include <iostream>


/*
宣告一個名稱為 cat 的類別
-----------------
變數:
    count 數量
    posx 紀錄x位置
    posy 紀錄y位置
-----------------
函數:
    set_value 設定數值
    get_count 回傳數量
    get_x 回傳x座標
    get_y 回傳y座標
    get_allcnt 回傳總數量
    isitme 檢查是否為正確的物件
    operator+ 重載運算值
-----------------
宣告一個名稱為 fatcat 的類別
-----------------
變數:
    count 數量
    posx 紀錄x位置
    posy 紀錄y位置
-----------------
函數:
    set_value 設定數值
    get_allcnt 回傳總數量
-----------------
*/
class fatcat;
class cat{
    public:
        
        void set_value(int, int, int);
        int get_count();
        int get_x();
        int get_y();
        static int get_allcnt();
        bool isitme(cat& param);
        cat operator +(cat);
        friend class fatcat;
    private:
        int count,posx,posy;
        static int cnt;
};

class fatcat{
    private:
        int count,posx,posy;
        static int cnt;
    public:
        static int get_allcnt();
        void set_value(cat& rv);

};

void cat::set_value(int a, int b, int c){
    count = a;
    cnt += count;
    posx = b;
    posy = c;
}

void fatcat::set_value(cat& rv){
    count = rv.count;
    cnt += rv.count;
    posx = rv.posx;
    posy = rv.posy;
}

int cat::get_count(){
    return count;
}

int cat::get_x(){
    return posx;
}

int cat::get_y(){
    return posy;
}

int cat::get_allcnt(){
    return cnt;
}

int fatcat::get_allcnt(){
    return cnt;
}

bool cat::isitme(cat& param){
    if(&param == this) return 1;
    else return 0;
}

cat cat::operator+(cat c){
    count = count + c.count;
    posx = posx + c.posx;
    posy = posy + c.posy;
    return *this;
}

int cat::cnt = 0;
int fatcat::cnt = 0;

int main ()
{
    cat c1,c2,c3;
    c1.set_value(1,1,2);
    c2.set_value(2,3,4);
    c3 = c1 + c2;
    cat* c4;
    c4  = &c3;
    if(c4->isitme(c3))
        std::cout << "c3 " << c4->get_count() << " " << c4->get_x() << " " << c4->get_y() << std::endl;
    std::cout << "all:" << cat::get_allcnt() << std::endl;

    fatcat fc1;
    fc1.set_value(c3);
    std::cout << fc1.get_allcnt() << std::endl;

}

---

Inheritance(繼承)

#include <iostream>


/*
宣告一個名稱為 allcat 的父類別
-----------------
變數:
    count 數量
    posx 紀錄x位置
    posy 紀錄y位置
-----------------
函數:
-----------------
宣告一個名稱為 cat 的子類別
-----------------
變數:
-----------------
函數:
    set_value 設定數值
    get_count 回傳數量
    get_x 回傳x座標
    get_y 回傳y座標
    get_allcnt 回傳總數量
    isitme 檢查是否為正確的物件
    operator+ 重載運算值
-----------------
宣告一個名稱為 fatcat 的子類別
-----------------
變數:
-----------------
函數:
    set_value 設定數值
    get_allcnt 回傳總數量
-----------------
*/
class allcat{
    protected:
        int count,posx,posy;
        static int cnt;
};
class fatcat;
class cat : private allcat{
    public:
        
        void set_value(int, int, int);
        int get_count();
        int get_x();
        int get_y();
        static int get_allcnt();
        bool isitme(cat& param);
        cat operator +(cat);
        friend class fatcat;
};

class fatcat : private allcat{
    public:
        static int get_allcnt();
        void set_value(cat& rv);

};

void cat::set_value(int a, int b, int c){
    count = a;
    cnt += count;
    posx = b;
    posy = c;
}

void fatcat::set_value(cat& rv){
    count = rv.count;
    cnt += rv.count;
    posx = rv.posx;
    posy = rv.posy;
}

int cat::get_count(){
    return count;
}

int cat::get_x(){
    return posx;
}

int cat::get_y(){
    return posy;
}

int cat::get_allcnt(){
    return cnt;
}

int fatcat::get_allcnt(){
    return cnt;
}

bool cat::isitme(cat& param){
    if(&param == this) return 1;
    else return 0;
}

cat cat::operator+(cat c){
    count = count + c.count;
    posx = posx + c.posx;
    posy = posy + c.posy;
    return *this;
}

int allcat::cnt = 0;

int main ()
{
    cat c1,c2,c3;
    c1.set_value(1,1,2);
    c2.set_value(2,3,4);
    c3 = c1 + c2;
    cat* c4;
    c4  = &c3;
    if(c4->isitme(c3))
        std::cout << "c3 " << c4->get_count() << " " << c4->get_x() << " " << c4->get_y() << std::endl;
    std::cout << "all:" << cat::get_allcnt() << std::endl;

    fatcat fc1;
    fc1.set_value(c3);
    std::cout << fc1.get_allcnt() << std::endl;

}

---

Pointers to Base Class(父類別指標)

#include <iostream>


/*
宣告一個名稱為 allcat 的父類別
-----------------
變數:
    count 數量
    get_allcnt 回傳總數量
    posx 紀錄x位置
    posy 紀錄y位置
-----------------
函數:
-----------------
宣告一個名稱為 cat 的子類別
-----------------
變數:
-----------------
函數:
    set_value 設定數值
    get_count 回傳數量
    get_x 回傳x座標
    get_y 回傳y座標
    isitme 檢查是否為正確的物件
    operator+ 重載運算值
-----------------
宣告一個名稱為 fatcat 的子類別
-----------------
變數:
-----------------
函數:
    set_value 設定數值
-----------------
*/
class allcat{
    public:
        int count,posx,posy;
        static int cnt;
        static int get_allcnt();
};
class fatcat;
class cat : public allcat{
    public:
        
        void set_value(int, int, int);
        int get_count();
        int get_x();
        int get_y();
        bool isitme(cat& param);
        cat operator +(cat);
        friend class fatcat;
};

class fatcat : public allcat{
    public:
        void set_value(cat& rv);

};

void cat::set_value(int a, int b, int c){
    count = a;
    cnt += count;
    posx = b;
    posy = c;
}

void fatcat::set_value(cat& rv){
    count = rv.count;
    cnt += rv.count;
    posx = rv.posx;
    posy = rv.posy;
}

int cat::get_count(){
    return count;
}

int cat::get_x(){
    return posx;
}

int cat::get_y(){
    return posy;
}

int allcat::get_allcnt(){
    return cnt;
}

bool cat::isitme(cat& param){
    if(&param == this) return 1;
    else return 0;
}

cat cat::operator+(cat c){
    count = count + c.count;
    posx = posx + c.posx;
    posy = posy + c.posy;
    return *this;
}

int allcat::cnt = 0;

int main ()
{
    
    cat c1,c2,c3;
    c1.set_value(1,1,2);
    c2.set_value(2,3,4);
    c3 = c1 + c2;
    cat* c4;
    c4  = &c3;
    allcat* c5 = &c1; 
    allcat* c6 = &c2;
    if(c4->isitme(c3))
        std::cout << "c3 " << c4->get_count() << " " << c4->get_x() << " " << c4->get_y() << std::endl;
    std::cout << "all:" << c5->get_allcnt() << std::endl;

    fatcat fc1;
    fc1.set_value(c3);
    std::cout << c6->get_allcnt() << std::endl;
}

---

Polymorphism：Virtual Members(虛擬成員)

#include <iostream>


/*
宣告一個名稱為 allcat 的父類別
-----------------
變數:
    
    count 數量
    posx 紀錄x位置
    posy 紀錄y位置
-----------------
函數:
    get_allcnt 回傳總數量
    get_count 回傳數量（虛擬）
-----------------
宣告一個名稱為 cat 的子類別
-----------------
變數:
-----------------
函數:
    set_value 設定數值
    get_count 回傳數量
    get_x 回傳x座標
    get_y 回傳y座標
    isitme 檢查是否為正確的物件
    operator+ 重載運算值
-----------------
宣告一個名稱為 fatcat 的子類別
-----------------
變數:
-----------------
函數:
    set_value 設定數值
    get_count 回傳數量
-----------------
*/
class allcat{
    public:
        int count,posx,posy;
        static int cnt;
        static int get_allcnt();
        virtual int get_count(void){ return 0; }
};
class fatcat;
class cat : public allcat{
    public:
        
        void set_value(int, int, int);
        int get_count();
        int get_x();
        int get_y();
        bool isitme(cat& param);
        cat operator +(cat);
        friend class fatcat;
};

class fatcat : public allcat{
    public:
        void set_value(cat& rv);
        int get_count();

};

void cat::set_value(int a, int b, int c){
    count = a;
    cnt += count;
    posx = b;
    posy = c;
}

void fatcat::set_value(cat& rv){
    count = rv.count;
    cnt += rv.count;
    posx = rv.posx;
    posy = rv.posy;
}

int cat::get_count(){
    return count;
}

int fatcat::get_count(){
    return count;
}


int cat::get_x(){
    return posx;
}

int cat::get_y(){
    return posy;
}

int allcat::get_allcnt(){
    return cnt;
}

bool cat::isitme(cat& param){
    if(&param == this) return 1;
    else return 0;
}

cat cat::operator+(cat c){
    count = count + c.count;
    posx = posx + c.posx;
    posy = posy + c.posy;
    return *this;
}

int allcat::cnt = 0;

int main ()
{
    
    cat c1,c2,c3;
    c1.set_value(1,1,2);
    c2.set_value(2,3,4);
    c3 = c1 + c2;
    cat* c4;
    c4  = &c3;
    allcat* c5 = &c1; 
    
    if(c4->isitme(c3))
        std::cout << "c3 " << c4->get_count() << " " << c4->get_x() << " " << c4->get_y() << std::endl;
    std::cout << "all:" << c5->get_allcnt() << std::endl;

    fatcat fc1;
    fc1.set_value(c3);
    allcat* c6 = &fc1;
    std::cout << c6->get_allcnt() << std::endl;
    std::cout << c5->get_count() << std::endl;
    std::cout << c6->get_count() << std::endl;
}

---

Polymorphism：Abstract Base Classes(抽象類別)

#include <iostream>


/*
宣告一個名稱為 allcat 的父類別
-----------------
變數:
    
    count 數量
    posx 紀錄x位置
    posy 紀錄y位置
-----------------
函數:
    get_allcnt 回傳總數量
    get_count 回傳數量（虛擬）
-----------------
宣告一個名稱為 cat 的子類別
-----------------
變數:
-----------------
函數:
    set_value 設定數值
    get_count 回傳數量
    get_x 回傳x座標
    get_y 回傳y座標
    isitme 檢查是否為正確的物件
    operator+ 重載運算值
-----------------
宣告一個名稱為 fatcat 的子類別
-----------------
變數:
-----------------
函數:
    set_value 設定數值
    get_count 回傳數量
-----------------
*/
class allcat{
    public:
        int count,posx,posy;
        static int cnt;
        static int get_allcnt();
        virtual int get_count(void)=0;
        void printcount(void){
            std::cout << this->get_count() << std::endl;
        }
};
class fatcat;
class cat : public allcat{
    public:
        
        void set_value(int, int, int);
        int get_count();
        int get_x();
        int get_y();
        bool isitme(cat& param);
        cat operator +(cat);
        friend class fatcat;
};

class fatcat : public allcat{
    public:
        void set_value(cat& rv);
        int get_count();

};

void cat::set_value(int a, int b, int c){
    count = a;
    cnt += count;
    posx = b;
    posy = c;
}

void fatcat::set_value(cat& rv){
    count = rv.count;
    cnt += rv.count;
    posx = rv.posx;
    posy = rv.posy;
}

int cat::get_count(){
    return count;
}

int fatcat::get_count(){
    return count;
}


int cat::get_x(){
    return posx;
}

int cat::get_y(){
    return posy;
}

int allcat::get_allcnt(){
    return cnt;
}

bool cat::isitme(cat& param){
    if(&param == this) return 1;
    else return 0;
}

cat cat::operator+(cat c){
    count = count + c.count;
    posx = posx + c.posx;
    posy = posy + c.posy;
    return *this;
}

int allcat::cnt = 0;

int main ()
{
    
    cat c1,c2,c3;
    c1.set_value(1,1,2);
    c2.set_value(2,3,4);
    c3 = c1 + c2;
    cat* c4;
    c4  = &c3;
    allcat* c5 = &c1; 
    
    if(c4->isitme(c3))
        std::cout << "c3 " << c4->get_count() << " " << c4->get_x() << " " << c4->get_y() << std::endl;
    std::cout << "all:" << c5->get_allcnt() << std::endl;

    fatcat fc1;
    fc1.set_value(c3);
    allcat* c6 = &fc1;
    std::cout << c6->get_allcnt() << std::endl;
    c5->printcount();
    c6->printcount();
}

---