Exception Handling syntax problems in a simple manner

Question

Note: I can't use anything that is default. I am trying to make a very simple exception handling routine or at the very least make something that looks the part. I don't want to do very much, just throw an exception and print an error message. in .h ``` class MyException { protected: string message; public: MyException (string mes) { this->message = mes; } MyException (); // is this necessary ? does it do anything ? string getMessage() const { return this->message; } }; ``` What I'd want is to have a "PersonException" and "ActivityException". Might use a template but not sure if that would work out. ``` class PersonException:public MyException { public: PersonException (string message):MyException(message) { } }; class PersonValidator { public: PersonValidator (Person p) throw (PersonException); }; ``` in .cpp ``` void PersonValidator::PersonValidator(Person p) throw (PersonException) { if (p.getPhone < 0) { throw PersonException ("Person Number is invalid"); } ``` What here is wrong…

Accepted Answer

1) The default constructor is not necessary, at least the way you have the code now, so you can remove

```
 MyException ();
```

2) It's recommended to derive exceptions from `std::exception`.

3) You can catch your exceptions by catching a `MyException&`, and print the message there :

```
try
{
    PersonValidator validator(Person());
}
catch(const MyException& ex)
{
    std::cout << ex.getMessage();
}
```

4) Avoid `using` directives in headers. Your syntax suggests you have a `using namespace std;` in the header. That's wrong, you should favor full name qualification, at least in headers:

```
protected: std::string message;
MyException (std::string mes)
```

etc.

5) Favor pass by const reference instead of pass by value, for complex types:

```
MyException (const std::string& mes)

PersonValidator (const Person& p)
```

6) Aim for const correctness:

```
std::string getMessage()
```

should be:

```
std::string getMessage() const
```

since it doesn't change any members.

7) Use initialization lists:

```
 MyException (string mes) {
     this->message = mes;
 }
```

becomes

```
 MyException (string mes) : message(mes) {
 }
```

Exception Handling syntax problems in a simple manner

Solution

Problem