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Program Repair Shop

45

Special cases

       169          foreach my $parent ( @parent_path ) {
       171              if ( $parent->isa( 'Class::Observable' ) ) {
       172                  push @observable_parents, $parent;
       173              }
       174          }

• Now what about line 171?

• Suppose Alarm has a base class that is not derived from Class::Observable?

• Say, class X

• But suppose we put X into @observable_parents anyway

What if we left out this special case?

• Well, in this case a problem

• Later on, we would try to call X->_obs_get_observers_scoped

• This would throw Can't locate object method ... via package "X"

• OK, fair enough

• But perhaps the right test is to add a guard condition to line 182:

       182          push @parent_observers, $parent->_obs_get_observers_scoped
                if $parent->can('_obs_get_observers_scoped');

• What do you think?

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