Softwareentwicklung in C++ - ASC

320 11. Exceptions
Außerdem gilt noch, dass immer der erste catch Block angesprungen wird,
der eine dieser Bedingungen erfüllt. Sollten also aus Gründen der Typenkompatibilität
mehrere catch Blöcke in Frage kommen, so wird der erste
davon genommen. Das bedeutet also, dass auch die Reihenfolge, in der die
catch Blöcke vorkommen, eine große Bedeutung spielt. Sehen wir uns das
am besten an einem Beispiel an (second_exception_demo.cpp):
1 // second exception demo . cpp − another demo , how the exception
2 // mechanism works in C++
3
4 #include
5 #include ” u s e r t y p e s . h”
6
7 using std : : cout ;
8 using std : : endl ;
9
10 //−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−
11 class Exception
12 {
13 public :
14 Exception ( ) { }
15 virtual ˜ Exception ( ) { }
16 } ;
17
18 //−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−
19 class DerivedAException : public virtual Exception
20 {
21 public :
22 DerivedAException ( ) { }
23 virtual ˜ DerivedAException ( ) { }
24 } ;
25
26 //−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−
27 class DerivedBException : public virtual Exception
28 {
29 public :
30 DerivedBException ( ) { }
31 virtual ˜ DerivedBException ( ) { }
32 } ;
33
34 //−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−
35 class DerivedCException : public DerivedAException
36 {
37 public :
38 DerivedCException ( ) { }
39 virtual ˜ DerivedCException ( ) { }
40 } ;
41
42 //−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−
43 class DerivedDException : public DerivedAException ,
44 public DerivedBException
45 {
46 public :
47 DerivedDException ( ) { }
48 virtual ˜ DerivedDException ( ) { }
49 } ;
50
51 //−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−
52 void demoFuncException ( )
53 throw( Exception )
54 {
55 throw Exception ( ) ;
56 }