c/c++语言开发共享c++-构造函数练习和delete，new

强化练习

 #include <stdio.h> #include <stdlib.h> #include <string.h> #include <iostream> #include <fstream> using namespace std;  class   abcd { public:     abcd(int    a, int  b, int  c)     {         _a = a;         _b = b;         _c = c;         printf("abcd()  construct,  a: %d,b: %d,c: %d        n", _a, _b, _c);     }     ~abcd()     {         printf("~abcd() construct,a: %d,b: %d,c: %d      n", _a, _b, _c);     }     int geta()     {         return  _a;     } private:     int _a;     int _b;     int _c; };  class   mye { public:      mye() :abcd1(1, 2, 3), abcd2(4, 5, 6), m(100)     {         cout << "mye()" << endl;     }     ~mye()     {         cout << "~mye()" << endl;     }      mye(const   mye &   obj) :abcd1(7, 8, 9), abcd2(10, 11, 12), m(100)     {         printf("myd(const   myd &   obj) n");     } public:     abcd    abcd1;   //c++编译器不知道如何构造abc1     abcd    abcd2;     const int   m; };  int dothing(mye mye1)//mye1.拷贝构造(main::mye) {     printf("dothing()   mye1.abc1.a: %d n", mye1.abcd1.geta());     return 0; } int run() {     mye mye;     dothing(mye);     return 0; }  int run2() {     printf("run2    start.. n");     //abcd(400, 500, 600);   //临时对象的⽣命周期             abcd    abcd    =   abcd(100,   200,    300);     printf("run2    endn");     return 0; }  int main(void) {     run2();     return 0; }

强化练习2

#include <stdio.h> #include <stdlib.h> #include <string.h> #include <iostream> #include <fstream> using namespace std;  //构造中调⽤构造是危险的⾏为 class   mytest { public:     mytest(int  a, int  b, int  c)     {         _a = a;         _b = b;         _c = c;     }     mytest(int  a, int  b)     {         _a = a;         _b = b;         mytest(a, b, 100);//创建一个匿名对象         //     }     ~mytest()     {         printf("mytest~: %d,     %d,     %dn", _a, _b, _c);     }     int getc()     {         return  _c;     }     void    setc(int    val)     {         _c = val;     }  private:     int _a;     int _b;     int _c; };  int main() {     mytest  t1(1, 2);     printf("c: %dn", t1.getc());    //请问c的值是？     return 0; } 

• 对象的动态构造和释放
  • malloc free函数，new delete 操作符号
  • 分配基础类型 、分配数组类型、分配对象
  • new和malloc 深入分析，混用测试、异同比较
• 匿名对象生命周期
• malloc free函数，new delete 操作符号
• 分配基础类型 、分配数组类型、分配对象
• new和malloc 深入分析，混用测试、异同比较
• 匿名对象总结
  • 匿名对象生命周期
  • 匿名对象去和留
  • 构造中调用构造
• 匿名对象去和留
• 构造中调用构造
• 静态成员变量和静态成员函数（属于类，语法）

new和delete

c与c++的比较

#define _crt_secure_no_warnings #include <stdio.h> #include <stdlib.h> #include <string.h> #include <iostream> #include <fstream>   using namespace std;  class test { public:     test()     {         cout << "test()" << endl;         m_a = 0;         m_b = 0;     }     test(int a, int b)     {         cout << "test(int, int)" << endl;         m_a = a;         m_b = b;     }     void printt()     {          cout << "printt:"<<m_a<<","<<m_b << endl;     }     ~test()     {         cout << "~test()" << endl;      } private:     int m_a;     int m_b; };  //c语言中 void test1() {     int *p = (int *)malloc(sizeof(int));      *p = 10;     if (p != null) {         free(p);         //delete p;         p = null;     }      int *array_p = (int *)malloc(sizeof(int)* 10);      for (int i = 0; i < 10; i++) {         array_p[i] = i + 1;     }      for (int i = 0; i < 10; i++) {         printf("%d ", array_p[i]);     }     printf("n");      if (array_p != null) {         free(array_p);         array_p = null;     }       cout << "==============" << endl;      test *tp = (test*)malloc(sizeof(test));     tp->printt();      if (tp != null) {         free(tp);         tp = null;     } }  //malloc free 是函数，标准库，stdlib.h //new 在堆上初始化一个对象的时候，会触发对象的构造函数。malloc不能 //free并不能触发一个对象的析构函数。 //c++中 void test2() {     int *p = new int;     *p = 10;     if (p != null) {         free(p);         p = null;     }      int *array_p = new int[10];     for (int i = 0; i < 10; i++) {         array_p[i] = i + 1;     }      for (int i = 0; i < 10; i++) {         cout << array_p[i]<<" ";     }     cout << endl;      if (array_p != null) {         delete [] array_p;     }      cout << "==========" << endl;     //test *tp = new test(10, 20);//触发有参构造     test *tp = new test;//触发无惨构造     tp->printt();     if (tp != null) {         delete tp;         tp = null;     }  }  int main(void) {     test1();      cout << "-----------" << endl;      test2();          return 0; }