类中是否可以定义 const 成员?
#include<stdio.h>
class Test
{
private:
const int ci = 0;
public:
int getCI() { return ci; }
};
int main()
{
Test t;
printf("t.ci = %d\n",t.getCI());
}
编译结果:
t20.cpp:13:10: error: uninitialized const member in ‘class Test’
Test t;
这时候引入本文的重点, 初始化列表出场:
ClassName::ClassName() :
m1(v1), m2(v1,v2),m3(v3)
{
//some other initialize operation
}
修改上述代码如下:
#include<stdio.h>
class Test
{
private:
const int ci;
public:
Test():ci(10)
{
//ci = 10;
}
int getCI() { return ci; }
};
int main()
{
Test t;
printf("t.ci = %d\n",t.getCI());
}
#include<stdio.h>
class Value
{
private:
int mi;
public:
Value(int i)
{
printf("i = %d\n",i) ;
mi = i;
}
int get()
{
return mi;
}
};
class Test
{
private:
const int ci;
Value m3;
Value m2;
Value m1;
public:
Test():m1(1),m2(2),m3(3),ci(100)
{
printf("Test::Test()\n");
}
int getCi()
{
return ci;
}
int setCi(int v)
{
int *p = const_cast<int *>(&ci);
*p = v;
}
};
int main()
{
Test t;
printf("t.ci = %d\n",t.getCi());
t.setCi(10);
printf("t.ci = %d\n",t.getCi());
return 0;
}
输出:
i = 3
i = 2
i = 1
Test::Test()
t.ci = 100
t.ci = 10