构造和析构的基础知识

对象的构造和析构
1.创建一个对象需要做初始化工作
构造函数
1)c++中的类可以定义和类同名的特殊成员函数，这种于类名相同的成员函数叫做析构函数
2)构造函数在定义时可以有参数
2)没有任何返回类型的声明
2.调用
自动
手动

析构函数
声明周期结束后自动调用
先创建的对象后释放

#include <iostream>class Test
{public:Test();void printP(void);~Test();private:int a;char* p;
};Test::Test()
{a = 10;p = (char*)malloc(100);strcpy(p, "aaafffafa");std::cout << "我是构造函数" << std::endl;
}void Test::printP(void)
{std::cout << a << std::endl;std::cout << p << std::endl;
}Test::~Test()
{if (p != NULL){free(p);}std::cout << "我是析构函数，我被调用了" << std::endl;
}void objplay()
{Test t1;t1.printP();std::cout << "先创建的对象后释放" << std::endl;Test t2;t2.printP();
}int main()
{objplay();std::cout << "Hello World!\n";
}

构造和析构的演示

#include <iostream>class Test
{public:Test();void printP(void);~Test();private:int a;char* p;
};Test::Test()
{a = 10;p = (char*)malloc(100);strcpy(p, "aaafffafa");std::cout << "我是构造函数" << std::endl;
}void Test::printP(void)
{std::cout << a << std::endl;std::cout << p << std::endl;
}Test::~Test()
{if (p != NULL){free(p);}std::cout << "我是析构函数，我被调用了" << std::endl;
}void objplay()
{Test t1;t1.printP();std::cout << "先创建的对象后释放" << std::endl;Test t2;t2.printP();
}int main()
{objplay();std::cout << "Hello World!\n";return 0;
}

构造函数的分类

#include <iostream>class Test2
{public:Test2();Test2(int a);Test2(int a, int b);Test2(const Test2& obj);void printT(void);~Test2();private:int m_a;int m_b;
};Test2::Test2()
{m_a = 0;m_b = 0;std::cout << "无参构造函数" << std::endl;
}Test2::Test2(int a)
{m_a = a;m_b = 0;std::cout << "无参构造函数" << std::endl;
}Test2::Test2(int a, int b)
{m_a = a;m_b = b;std::cout << "有参构造函数" << std::endl;
}Test2::Test2(const Test2& obj)
{std::cout << "我也是构造函数" << std::endl;
}void Test2::printT(void)
{std::cout << "我是普通成员函数" << std::endl;
}Test2::~Test2()
{}void objplay2()
{Test2 t1;t1.printT();Test2 t2(1, 2);t2.printT();Test2 t3 = (1, 2);t3.printT();Test2 t4 = Test2(1, 2);t4.printT();}int main2()
{objplay2();std::cout << "Hello World!\n";return 0;
}

构造和析构的综合练习

#include <iostream>class ABCD
{public:ABCD(int a, int b, int c);~ABCD();
public:int getA();private:int a;int b;int c;
};ABCD::ABCD(int a, int b, int c)
{this->a = a;this->b = b;this->c = c;std::cout << "ABCD() construct,a:" << this->a << "b:" << this->b << "c:" << this->c << std::endl;
}ABCD::~ABCD()
{std::cout << "~ABCD() construct,a:" << this->a << "b:" << this->b << "c:" << this->c << std::endl;
}int ABCD::getA()
{return this->a;
}class MyE
{public:MyE();MyE(const MyE& obj);~MyE();public:ABCD abcd1;ABCD abcd2;const int m;
private:
};MyE::MyE() :abcd1(1, 2, 3), abcd2(4, 5, 6), m(100)
{}MyE::MyE(const MyE& obj) : abcd1(7, 8, 9), abcd2(10, 11, 12), m(100)
{std::cout << "MyE(const My & obj)" << std::endl;
}MyE::~MyE()
{std::cout << "MyE()" << std::endl;
}int doThing(MyE mye1)
{std::cout << "doThing() mye1.abc1.a" << mye1.abcd1.getA() << std::endl;return 0;
}int run2()
{MyE myE;doThing(myE);return 0;
}int run3()
{std::cout << "run3 start.." << std::endl;//ABCD(400, 500, 600);ABCD abcd = ABCD(100, 200, 300);std::cout << "run3 end.." << std::endl;return 0;
}int main3311()
{//run2();run3();std::cout << "Hello World" << std::endl;return 0;
}

构造函数调用规则研究

#include <iostream>class Test_1
{public:Test_1();Test_1(int a, int b);Test_1(const Test_1& obj);void printT();private:int m_a;int m_b;
};Test_1::Test_1()
{m_a = 0;m_b = 0;
}Test_1::Test_1(int a, int b)
{m_a = a;m_b = b;
}Test_1::Test_1(const Test_1& obj)
{m_a = obj.m_a;m_b = obj.m_b;
}void Test_1::printT()
{}void object_play24()
{Test_1 t1;
}int main621()
{object_play24();std::cout << "Hello World!\n";return 0;
}

copy构造函数的调用时机


#include <iostream>class Test4
{public:Test4();Test4(int a, int b);Test4(const Test4& obj);void printT();~Test4();private:int m_a;int m_b;
};Test4::Test4()
{m_a = 0;m_b = 0;std::cout << "我是构造函数" << std::endl;
}Test4::Test4(int a, int b)
{m_a = a;m_b = b;
}Test4::Test4(const Test4& obj)
{std::cout << "我也是构造函数" << std::endl;m_a = obj.m_a + 100;m_b = obj.m_b + 100;
}void Test4::printT()
{std::cout << "我是普通成员函数" << std::endl;std::cout << "m_a: " << m_a << std::endl;std::cout << "m_b: " << m_b << std::endl;
}Test4::~Test4()
{std::cout << "我是析构函数" << std::endl;
}int main4()
{Test4 t1(1, 2);Test4 t0(1, 2);t0 = t1;/*Test4 t2 = t1;t2.printT();*/Test4 t2(t1);t2.printT();std::cout << "Hello World!\n";return 0;
}

copy构造函数

#include <iostream>class Location
{public:Location(int x = 0, int y = 0);Location(const Location& obj);~Location();public:int getX();int getY();private:int m_x;int m_y;
};Location::Location(int x, int y)
{m_x = x;m_y = y;std::cout << "Constructor Object." << std::endl;
}Location::Location(const Location& obj)
{m_x = obj.m_x;m_y = obj.m_y;
}int Location::getX()
{return m_x;
}int Location::getY()
{return m_y;
}Location::~Location()
{std::cout << "Object Destroyed." << std::endl;
}void f(Location p)
{std::cout << p.getX() << std::endl;std::cout << p.getY() << std::endl;
}void object_play()
{Location a(1, 2);Location b = a;f(b);//b实参去初始化p，会调用拷贝构造函数
}int main5()
{object_play();std::cout << "Hello World!\n";return 0;
}

拷贝构造函数的第四种应用场景

#include <iostream>class Location1
{public:Location1(int x = 0, int y = 0);Location1(const Location1& obj);~Location1();public:int getX();int getY();private:int m_x;int m_y;
};Location1::Location1(int x, int y)
{m_x = x;m_y = y;std::cout << "Constructor Object." << std::endl;
}Location1::Location1(const Location1& obj)
{m_x = obj.m_x;m_y = obj.m_y;
}int Location1::getX()
{return m_x;
}int Location1::getY()
{return m_y;
}Location1::~Location1()
{std::cout << "Object Destroyed." << std::endl;
}void f(Location1 p)
{std::cout << p.getX() << std::endl;std::cout << p.getY() << std::endl;
}//返回一个元素
Location1 g()
{Location1 A(1, 2);return A;
}void object_play21()
{g();
}void object_play22()
{Location1 m = g();//匿名对象不析构  初始化
}void object_play23()
{Location1 m2(1, 2);m2 = g();//匿名对象 被析构  赋值
}int main61()
{object_play23();std::cout << "Hello World!\n";return 0;
}

构造函数的调用规则

#include <iostream>class Test_1
{public:Test_1();Test_1(int a, int b);Test_1(const Test_1& obj);void printT();private:int m_a;int m_b;
};Test_1::Test_1()
{m_a = 0;m_b = 0;
}Test_1::Test_1(int a, int b)
{m_a = a;m_b = b;
}Test_1::Test_1(const Test_1& obj)
{m_a = obj.m_a;m_b = obj.m_b;
}void Test_1::printT()
{}void object_play24()
{Test_1 t1;
}int main621()
{object_play24();std::cout << "Hello World!\n";return 0;
}

浅拷贝和深拷贝分析

#include <iostream>class Name
{public:Name();Name(const char *my);Name(const Name& obj);~Name();private:char* p;int len;
};Name::Name()
{p = NULL;len = 0;
}Name::Name(const char* myp)
{len = strlen(myp);myp = (char*)malloc(len + 1);strcpy(p, myp);
}Name::Name(const Name& obj)
{len = obj.len;p = (char*)malloc(len + 1);strcpy(p, obj.p);
}Name::~Name()
{if (p != NULL){free(p);p = NULL;len = 0;}
}void obj_play_y()
{Name obj1("asodfa");Name obj2 = obj1;Name obj3("obj3");obj3 = obj1;  //浅拷贝  等号赋值  显示重载等号操作符
}int main27()
{obj_play_y();std::cout << "Hello World" << std::endl;return 0;
}

构造函数的初始化列表

#include <iostream>class A
{public:A(int  _a);~A();private:int a;
};A::A(int _a)
{a = _a;std::cout << "构造函数a：" << a << std::endl;
}A::~A()
{std::cout << "析构函数a：" << a << std::endl;
}class B
{public:B(int _b1, int _b2, int m, int n);~B();private:int b1;int b2;A a1;A a2;const int c;
};B::B(int _b1, int _b2, int m, int n) : a1(m), a2(n) , c(0)
{b1 = _b1;b2 = _b2;}B::~B()
{std::cout << "析构函数B：" << std::endl;
}void playObj()
{//参数传递;B objB(1, 2, 3, 4);//调用顺序// 构造函数  如果子和对象有多个，按照定义顺序 不是初始化列表顺序// 析构函数  和构造函数相反
}int main190()
{playObj();std::cout << "Hello World" << std::endl;return 0;
}

new 和 delete 的用法

基本语法

#include <iostream>int main1301()
{int* a = (int*)malloc(sizeof(int));*a = 10;//int* p = new int;*p = 20;free(p);int *p1 = new int(30);delete p1;std::cout << "Hello World" << std::endl;return 0;
}
//分配数组
int main1302()
{int* p = (int*)malloc(sizeof(int) * 10); //int array[10];p[0] = 1;free(p);//c++ 分配数组int* pArray = new int[10];pArray[1] = 2;delete[] pArray; //数组加[]std::cout << "Hello World" << std::endl;return 0;
}class MyTest
{public:MyTest(int a);~MyTest();private:int a;
};MyTest::MyTest(int a)
{this->a = a;std::cout << "构造函数执行" << std::endl;
}MyTest::~MyTest()
{std::cout << "析构函数执行" << std::endl;
}//分配对象
int main13221()
{//c 语言MyTest* pT1 = (MyTest*)malloc(sizeof(MyTest));free(pT1);//c++MyTest* pT2 = new MyTest(10);delete pT2;std::cout << "Hello World" << std::endl;return 0;
}

深入分析

#include <iostream>int main13021()
{int* a = (int*)malloc(sizeof(int));*a = 10;//int* p = new int;*p = 20;delete p;//free(p);int* p1 = new int(30);delete p1;std::cout << "Hello World" << std::endl;return 0;
}
//分配数组
int main122321()
{int* p = (int*)malloc(sizeof(int) * 10); //int array[10];p[0] = 1;//free(p);delete[] p;//c++ 分配数组int* pArray = new int[10];pArray[1] = 2;//delete[] pArray; //数组加[]delete[] pArray;std::cout << "Hello World" << std::endl;return 0;
}class MyTest1
{public:MyTest1(int a);~MyTest1();private:int a;
};MyTest1::MyTest1(int a)
{this->a = a;std::cout << "构造函数执行" << std::endl;
}MyTest1::~MyTest1()
{std::cout << "析构函数执行" << std::endl;
}//分配对象
int main1401()
{//c 语言MyTest1* pT1 = (MyTest1*)malloc(sizeof(MyTest1));delete(pT1);//c++MyTest1* pT2 = new MyTest1(10);free(pT2);std::cout << "Hello World" << std::endl;return 0;
}

静态成员变量和静态成员函数

#include <iostream>class BB
{public:BB();~BB();
public:int getC();static void getCC();int AddC();private:int a;int b;static int c;
};BB::BB()
{}BB::~BB()
{}int BB::getC()
{return c;
}void BB::getCC()
{std::cout << "c:" << c << std::endl;
}int BB::AddC()
{return c++;
}int BB::c = 10;int main123346534()
{BB b1, b2, b3;std::cout << b1.getC() << std::endl;b2.AddC();std::cout << b3.getC() << std::endl;b3.getCC();BB::getCC();std::cout << "Hello World" << std::endl;return 0;
}

this 指针

#include <iostream>class TTest
{public:TTest(int a, int b);  //Test(Test* this, int a, int b)~TTest();
public:void printT();private:int a;int b;
};TTest::TTest(int a, int b)
{this->a = a;this->b = b;
}TTest::~TTest()
{}void TTest::printT()
{std::cout << "a" << a << std::endl;std::cout << "b" << b << std::endl;
}int main113322()
{TTest tt1(1, 2);tt1.printT();std::cout << "Hello World" << std::endl;return 0;
}

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c++基础day03

c++基础练习

构造和析构的基础知识

构造和析构的演示

构造函数的分类

构造和析构的综合练习

构造函数调用规则研究

copy构造函数的调用时机

copy构造函数

拷贝构造函数的第四种应用场景

构造函数的调用规则

浅拷贝和深拷贝分析

构造函数的初始化列表

new 和 delete 的用法

基本语法

深入分析

静态成员变量和静态成员函数

this 指针

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