C++ 构造函数深入理解
01_初始化参数列表.cpp
#includeint i,const char*n, int a,int s):id(i),age(a),score(s)
{
cout<<"student "<" construction!"<if(n){
name =(char*)malloc(strlen(n)+1);
strcpy(name,n);
}
}
//拷贝构造函数定义
//拷贝构造函数的有效参数，必须是该类的对象的引用
#if 1
// Student(Student & s,int class_no=1){
Student(Student & s){
cout<<"student "<" copy construction!"<#if 1
if(s.name){
name =(char*)malloc(strlen(s.name)+1);
strcpy(name,s.name);
}
#else
name = s.name;
#endif
age=s.age;score=s.score;
}
#endif
~Student()
{
cout<<"student "<" destructor!"<if(name)free(name);
}
};//end class Student
int get_stu_age(Student &s)
{
return s.age;
}
Student stu1(1001,"lisi",20,100);
Student & get_stu()
{
return stu1;
}
//如果函数的参数和返回值是类类型的对象，那么在实参传递和函数返回时，会发生拷贝构造函数的调用;
//如果想避免此类调用带来的巨大开销，可以使用引用
int main()
{
// Student stu2 = stu1;
cout<return 0;
}
02_default.cpp
#include" construction!"<if(n){
name =(char*)malloc(strlen(n)+1);
strcpy(name,n);
}
age=a;score=s;
}
//拷贝构造函数定义
//拷贝构造函数的有效参数，必须是该类的对象的引用
#if 1
// Student(Student & s,int class_no=1){
Student(Student & s){
cout<<"student "<" copy construction!"<#if 1
if(s.name){
name =(char*)malloc(strlen(s.name)+1);
strcpy(name,s.name);
}
#else
name = s.name;
#endif
age=s.age;score=s.score;
}
#endif
~Student()
{
cout<<"student "<" destructor!"<if(name)free(name);
}
};//end class Student
int get_stu_age(Student &s)
{
return s.age;
}
Student stu1(1001,"lisi",20,100);
Student & get_stu()
{
return stu1;
}
//如果函数的参数和返回值是类类型的对象，那么在实参传递和函数返回时，会发生拷贝构造函数的调用;
//如果想避免此类调用带来的巨大开销，可以使用引用
int main()
{
// Student stu2 = stu1;
cout<return 0;
}
03_deleted.cpp
#include" construction!"<if(n){
name =(char*)malloc(strlen(n)+1);
strcpy(name,n);
}
age=a;score=s;
}
Student(Student & s){
cout<<"student "<" copy construction!"<if(s.name){
name =(char*)malloc(strlen(s.name)+1);
strcpy(name,s.name);
}
age=s.age;score=s.score;
}
//delete是禁止某类参数传递的构造函数使用
Student(const string s)=delete;
/*
{
strcpy(name,s.c_str());
}*/
~Student()
{
cout<<"student "<" destructor!"<if(name)free(name);
}
};//end class Student
int main()
{
Student s("lisi");
return 0;
}
04_explicit.cpp
#include
id=i;
if(n){
name =(char*)malloc(strlen(n)+1);
strcpy(name,n);
}
age=a;score=s;
}
//explicit要求构造函数必须直接初始化的方式调用，不允许隐式转换
// explicit
Student(const Student & s){
// cout<<"student "<
id=s.id;
if(s.name){
name =(char*)malloc(strlen(s.name)+1);
strcpy(name,s.name);
}
age=s.age;score=s.score;
}
//delete是禁止某类参数传递的构造函数使用
Student(const char* n)
{
if(n){
name=(char*)malloc(strlen(n)+1);
strcpy(name,n);
}
}
~Student()
{
// cout<<"student "<
if(name)free(name);
}
explicit void show_stu_name(const Student &s)
{
cout<//end class Student
int main()
{
Student s1(1001,"lisi",20,100);
s1.show_stu_name(Student(Student("lisi")));
// Student s2 = s1;
Student s2(s1);
// Student s3 = s1;
return 0;
}
05_多参数初始化.cpp
#include::iterator it=l.begin();;
for(auto k:l)
{
cout<" ";
if(i ==0)a =k;
if( i==2)c=k;
if(i==4)e=k;
i++;
}
cout<int main()
{
int k{10};
cout<1,2,3,4,5};
cout<0]<for(auto k:a.m)
cout<" ";
cout<1,2,3,4,5};
cout<<"b.a="<cout<<"b.b="<cout<<"b.c="<cout<<"b.d="<cout<<"b.e="<5,6,7,8,9};
cout<cout<cout<return 0;
}