2018-03-23

1.struct内不能定义成员函数

include

struct s
{
int x; //正确
void print(); //错误
};
int main()
{}
错误：字段‘print’声明为一个函数
void print();

2.struct成员默认为public， class成员默认为private

include

include

struct s
{
int x;
char name[20];
}s1;
int main()
{
s1.x=18;
strcpy(s1.name, "bzz"); //正确
printf("%s:%d\n", s1.name, s1.x);
}
输出：bzz:18

include

using namespace std;

class s
{
int x;
}s1;

int main()
{
s1.x=5; //错误
}
报错：
test.cpp:6:6: 错误：‘int s::x’是私有的
int x;
^
test.cpp:11:5: 错误：在此上下文中
s1.x=5;

3.struct不可以设为空 class 可以

include

include

struct s
{
int x;
char name[20];
}s1;
int main()
{
struct s *s2=NULL; //错误
}
报错：
test.c: 在函数‘main’中:
test.c:10:9: 错误：无效的初始值设定
struct s s2=NULL;

4.class可以定义析构器，但是struct不可以

include

include

struct CTest
{
CTest();
~CTest(); //错误
int num;
};
int main()
{
}
报错：
test.c:5:5: 错误：expected specifier-qualifier-list before ‘CTest’
CTest();
^

5. class可以有显式的无参构造器，但是struct不可以
   public struct structA
   {
   //public int A = 90; //错误:“structA.A”: 结构中不能有实例字段初始值
   public int A;
   //public structA() //错误:结构不能包含显式的无参数构造函数
   //{
   // this.A = 0;
   //}

   public structA(int paraA) //ok
   {
   this.A = paraA;
   }
   }

public class classA
{
public int A = 90;
public classA()
{
this.A = 90;
}
}