代码中的这个错误是什么？

Question

在使用 try-catch 时遇到了这个错误。但我无法查出这个错误的原因，尽管我上网冲浪 所以。

我的代码是......

int main()
{
Queue q;
int choice,data;

 while(1)
 {
  choice  = getUserOption();
  switch(choice)
  {
   case 1:
     cout<<"\nEnter an element:";
     cin>>data;
     q.enqueue(data);
     break;
   case 2:
     int element;
     element = q.dequeue();
     cout<<"Element Dequeued:\n"<<element;
     break;
   case 3:
     q.view();
     break;
   case 4:
     exit(EXIT_SUCCESS);
  }
  catch(UnderFlowException e)
  {
   cout<<e.display();
  }
  catch(OverFlowException e)
  {
   cout<<e.display();
  }

 }// end of while(1)

       return 0;
}

对我来说，上面代码中的所有内容似乎都是正确的。但是 g++ 编译器正在抛出......

muthu@muthu-G31M-ES2L:~/LangFiles/cppfiles/2ndYearLabException$ g++ ExceptionHandlingEdited.cpp
ExceptionHandlingEdited.cpp: In member function ‘void Queue::enqueue(int)’:
ExceptionHandlingEdited.cpp:89:97: warning: deprecated conversion from string constant to ‘char*’
ExceptionHandlingEdited.cpp: In member function ‘int Queue::dequeue()’:
ExceptionHandlingEdited.cpp:113:95: warning: deprecated conversion from string constant to ‘char*’
ExceptionHandlingEdited.cpp: In member function ‘void Queue::view()’:
ExceptionHandlingEdited.cpp:140:66: warning: deprecated conversion from string constant to ‘char*’
ExceptionHandlingEdited.cpp: In function ‘int main()’:
ExceptionHandlingEdited.cpp:185:3: error: expected primary-expression before ‘catch’
ExceptionHandlingEdited.cpp:185:3: error: expected ‘;’ before ‘catch’
ExceptionHandlingEdited.cpp:189:3: error: expected primary-expression before ‘catch’
ExceptionHandlingEdited.cpp:189:3: error: expected ‘;’ before ‘catch’

Answer 1

如果没有 try，就不可能有 catch。将行：

try {

放在 while 语句之前。

如果您想消除有关字符串常量的警告，您可能必须将类型更改为 const char * 或显式转换/复制它们。或者您可以使用 gcc 的 -Wno-write-strings 选项。

Answer 2

您需要将代码包含在 try {...} 构造中，否则 catch 将不知道它应该捕获什么代码。

将 while 循环包装到 try 中：

try {
 while(1)
   {
    .....
   }// end of while(1)
} catch(UnderFlowException e) ...

参考。

Answer 3

试试这个：

int main()
{
Queue q;
int choice,data;

 while(1)
 {
  choice  = getUserOption();
  try 
  {
    switch(choice)
    {
     case 1:
       cout<<"\nEnter an element:";
       cin>>data;
       q.enqueue(data);
       break;
     case 2:
       int element;
       element = q.dequeue();
       cout<<"Element Dequeued:\n"<<element;
       break;
     case 3:
       q.view();
       break;
     case 4:
       exit(EXIT_SUCCESS);
    }
  }
  catch(UnderFlowException e)
  {
   cout<<e.display();
  }
  catch(OverFlowException e)
  {
   cout<<e.display();
  }

 }// end of while(1)

       return 0;
}