做QT出现的问题

当我在first.cpp中加入int z,x,y后，然后
void first::user_button22()
{
    int i=0,a;
    switch ( p )
    {
     case '+':
          z=x+y;
          break;
     case '-':
          z=x-y;
          break;
     case 'x':
          z=x*x;
          break;
     case '*':
          z=x*y;
          break;
     case '/':
          z=x/y;
          break;
    }
其中有+号后，编译就出现了如下错误
first.cpp:245: invalid use of member (did you forget the `&' ?)
first.cpp:245: invalid use of member (did you forget the `&' ?)
first.cpp:248: invalid use of member (did you forget the `&' ?)
first.cpp:248: invalid use of member (did you forget the `&' ?)
first.cpp:251: invalid use of member (did you forget the `&' ?)
first.cpp:251: invalid use of member (did you forget the `&' ?)
first.cpp:254: invalid use of member (did you forget the `&' ?)
first.cpp:254: invalid use of member (did you forget the `&' ?)

贴的代码不完整，不够我觉得应该如果p是字符指针的话，前面要加&来解引用

245行指的是源码的哪一行啊？