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原版要求：
class Fruit{
int no;
double weight;
char key;
public:
void print() { }
virtual void process(){ }
};
class Apple: public Fruit{
int size;
char type;
public:
void save() { }
virtual void process(){ }
};
爲上週題目中的 Fruit和Apple 添加 構造函數與 析構函數， 並在構造函數與析構函數中打印控制檯信息，觀察構造和析枸調用過程。然後爲Apple類重載::operator new和 ::operator delete，在控制檯打印信息，並觀察調用結果。
先回憶一下new和delete
而new和delete是不可以重載的，只能重載operator new和operator delete
而要new和delete首先要有對應的構造函數和析構函數
Fruit() :no(0), weight(0), key('\0') { cout << "guo::Fruit::defaule ctor.this=" << this << " no=" << no << " weight=" << weight << " key=" << key << endl; }
Fruit(int no_1, double weight_1, char key_1) :no(no_1), weight(weight_1), key(key_1)
{
cout << "guo::Fruit::ctor.this=" << this << " no=" << no << " weight=" << weight << " key=" << key << endl;
}
~Fruit() { cout << "guo::Fruit::dtor.this=" << this << " no=" << no << " weight=" << weight << " key=" << key << endl; }
Apple() :size(0), type(0) { cout << "guo::Apple::defaule ctor.this=" << this << " size=" << size << " type=" << type << endl; }
Apple(int size_1, char type_1) :size(size_1), type(type_1)
{
cout << "guo::Apple::ctor.this=" << this << " size=" << size << " type=" << type << endl;
}
~Apple() { cout << "guo::Apple::dtor.this=" << this << " size=" << size << " type=" << type << endl; }
子類構造函數會先調用父類的默認構造函數，然後在調用對應的構造函數
子類對象聲明週期結束後會調用析構函數，而讓他顯示到dos窗口最簡單的辦法就是delete,調用delete時會先調用子類析構函數，然後是父類析構，最後纔是operator delete.
然後我在類裏聲明靜態重載
class Fruit
{
private:
int no;
double weight;
char key;
public:
Fruit() :no(0), weight(0), key('\0') { cout << "guo::Fruit::defaule ctor.this=" << this << " no=" << no << " weight=" << weight << " key=" << key << endl; }
Fruit(int no_1, double weight_1, char key_1) :no(no_1), weight(weight_1), key(key_1)
{
cout << "guo::Fruit::ctor.this=" << this << " no=" << no << " weight=" << weight << " key=" << key << endl;
}
~Fruit() { cout << "guo::Fruit::dtor.this=" << this << " no=" << no << " weight=" << weight << " key=" << key << endl; }
const int get_no() const { return no; }
const double get_weight() const { return weight; }
const char get_key() const { return key; }
virtual void print() const { cout << "guo::Fruit::print.this=" << this << " no=" << no << " weight=" << weight << " key=" << key << endl; }
virtual void process(){ }
};
class Apple : public Fruit{
private:
int size;
char type;
public:
Apple() :size(0), type(0) { cout << "guo::Apple::defaule ctor.this=" << this << " size=" << size << " type=" << type << endl; }
Apple(int size_1, char type_1) :size(size_1), type(type_1)
{
cout << "guo::Apple::ctor.this=" << this << " size=" << size << " type=" << type << endl;
}
~Apple() { cout << "guo::Apple::dtor.this=" << this << " size=" << size << " type=" << type << endl; }
static void* operator new(size_t size);
static void operator delete(void* pdead, size_t size);
static void* operator new[](size_t size);
static void operator delete[](void* pdead, size_t size);
void save() { }
const int get_size() const { return size; }
const char get_type() const { return type; }
virtual void print() const { cout << "guo::Apple::print.this=" << this << " size=" << size << " type=" << type << endl; }
virtual void process() { }
};
operator new和operator new[] 除了名稱之外函數內的自定義操作是一樣的,operator delete和operator delete[]操作也是一樣的
在這裏我用了異常處理語句try 和 catch
inline void* Apple::operator new(size_t size)
{
Apple* p;
try
{
p = (Apple*)malloc(size);
}
catch(bad_alloc& e)
{
cout << "內存不足無法調用Apple::void* operator new(size_t size)" << endl;
delete p;
return 0;
}
cout << "調用Apple::void* operator new(size_t size)，" << "size=" << size << endl;
return p;
}
inline void Apple::operator delete(void* pdead, size_t size)
{
cout << "調用Apple::void operator delete(void* pdead, size_t size)，" << "pdead=" << pdead << " size=" << size << endl;
free(pdead);
}
inline void* Apple::operator new[](size_t size)
{
Apple* p;
try
{
p = (Apple*)malloc(size);
}
catch (bad_alloc& e)
{
cout << "內存不足無法調用Apple::void* operator new[](size_t size)" << endl;
delete p;
return 0;
}
cout << "調用Apple::void* operator new[](size_t size)，" << "size=" << size << endl;
return p;
}
inline void Apple::operator delete[](void* pdead, size_t size)
{
cout << "調用Apple::void operator delete[](void* pdead, size_t size)，" << "pdead=" << pdead << " size=" << size << endl;
free(pdead);
}
全部代碼：
/* fruit.h */
/* 本程序在vs2013運行測試成功 */
#ifndef __FRUIT_H__
#define __FRUIT_H__
namespace guo
{
#include<iostream>
using namespace std;
class Fruit
{
private:
int no;
double weight;
char key;
public:
Fruit() :no(0), weight(0), key('\0') { cout << "guo::Fruit::defaule ctor.this=" << this << " no=" << no << " weight=" << weight << " key=" << key << endl; }
Fruit(int no_1, double weight_1, char key_1) :no(no_1), weight(weight_1), key(key_1)
{
cout << "guo::Fruit::ctor.this=" << this << " no=" << no << " weight=" << weight << " key=" << key << endl;
}
~Fruit() { cout << "guo::Fruit::dtor.this=" << this << " no=" << no << " weight=" << weight << " key=" << key << endl; }
const int get_no() const { return no; }
const double get_weight() const { return weight; }
const char get_key() const { return key; }
virtual void print() const { cout << "guo::Fruit::print.this=" << this << " no=" << no << " weight=" << weight << " key=" << key << endl; }
virtual void process(){ }
};
class Apple : public Fruit{
private:
int size;
char type;
public:
Apple() :size(0), type(0) { cout << "guo::Apple::defaule ctor.this=" << this << " size=" << size << " type=" << type << endl; }
Apple(int size_1, char type_1) :size(size_1), type(type_1)
{
cout << "guo::Apple::ctor.this=" << this << " size=" << size << " type=" << type << endl;
}
~Apple() { cout << "guo::Apple::dtor.this=" << this << " size=" << size << " type=" << type << endl; }
static void* operator new(size_t size);
static void operator delete(void* pdead, size_t size);
static void* operator new[](size_t size);
static void operator delete[](void* pdead, size_t size);
void save() { }
const int get_size() const { return size; }
const char get_type() const { return type; }
virtual void print() const { cout << "guo::Apple::print.this=" << this << " size=" << size << " type=" << type << endl; }
virtual void process() { }
};
inline void* Apple::operator new(size_t size)
{
Apple* p;
try
{
p = (Apple*)malloc(size);
}
catch(bad_alloc& e)
{
cout << "內存不足無法調用Apple::void* operator new(size_t size)" << endl;
delete p;
return 0;
}
cout << "調用Apple::void* operator new(size_t size)，" << "size=" << size << endl;
return p;
}
inline void Apple::operator delete(void* pdead, size_t size)
{
cout << "調用Apple::void operator delete(void* pdead, size_t size)，" << "pdead=" << pdead << " size=" << size << endl;
free(pdead);
}
inline void* Apple::operator new[](size_t size)
{
Apple* p;
try
{
p = (Apple*)malloc(size);
}
catch (bad_alloc& e)
{
cout << "內存不足無法調用Apple::void* operator new[](size_t size)" << endl;
delete p;
return 0;
}
cout << "調用Apple::void* operator new[](size_t size)，" << "size=" << size << endl;
return p;
}
inline void Apple::operator delete[](void* pdead, size_t size)
{
cout << "調用Apple::void operator delete[](void* pdead, size_t size)，" << "pdead=" << pdead << " size=" << size << endl;
free(pdead);
}
}
#endif
/* fruit.h */
/* 本程序在vs2013運行測試成功 */
#include<iostream>
#include"fruit.h"
using namespace std;
int main()
{
cout << "sizeof(Fruit)=" << sizeof(guo::Apple) << endl << endl;
cout << "測試guo::Fruit::Fruit()構造函數:" << endl;
guo::Fruit f1;
cout << endl<<"測試guo::Fruit::Fruit(int no_1, double weight_1, char key_1)構造函數:" << endl;
guo::Fruit f2{ 1, 1, 'a' }; //{} 初始化不容易產生歧義
cout << endl<<"測試guo::Apple::Apple()構造函數:" << endl;
guo::Apple a1;
cout << endl << "測試guo::Apple::Apple(int size_1, char type_1)()構造函數:" << endl;
guo::Apple a2{ 5, 'a' };
cout << endl << "測試guo::void* Apple::operator new(size_t size)重載函數:" << endl;
guo::Apple* p1 = new guo::Apple{ 6, 'b' };
cout << endl << "測試 全局 ::operator new 函數:" << endl;
guo::Apple* px1 = ::new guo::Apple{ 6, 'b' };
cout << endl << "測試guo::void Apple::operator delete(void* pdead, size_t size)重載函數 及 Fruit、Apple析構函數:" << endl;
delete p1;
cout << endl << "測試 全局 ::operator delete 函數 及 Fruit、Apple析構函數:" << endl;
::delete px1;
cout << endl << "測試guo::void* Apple::operator new[](size_t size)重載函數:" << endl;
guo::Apple* p2 = new guo::Apple[5];
cout << endl << "測試 全局 ::operator new[] 函數:" << endl;
guo::Apple* px2 = ::new guo::Apple[5];
cout << endl << "測試guo::void Apple::operator delete[](void* pdead, size_t size)重載函數 及 Fruit、Apple析構函數:" << endl;
delete[] p2;
cout << endl << "測試 全局 ::operator delete[] 函數 及 Fruit、Apple析構函數:" << endl;
::delete[] px2;
getchar();
return 0;
}
