c++ - Inheritance: use inherited methods from parent pointer -

-

i'm working production code, of cannot safely modify (without breaking things). issue use specific method, 1 of parameters of pointer class. class parameter not want to.

so wrote sub-class of class , attempting call above function, still uses parent class' methods.

i have mwe below:

#include <iostream>  class parent  { public:     parent() {};     void method() {std::cout<<"in parent\n";} };  class child : public parent { public:     child() {};     void method() {std::cout<<"in child\n";} };  void secondmethod(parent* pptr) {     pptr->method(); }  int main() {     child c = child();     parent* parentptr = &c;      c.method();     parentptr->method();      secondmethod(parentptr);     secondmethod(&c);      return 0; }

in above example running output of course:

in child in parent in parent in parent

i believe issue slicing? i'm casting pointer of parent class, considered parent.

i have seen ways around making methods virtual in parent class don't have option.

is there way make secondmethod actual use child's method? without changing parent class or secondmethod.

no not if aren't able change parent class or 'secondmethod'. constructor of 'secondmethod' defines parameter parent*. passing child* 'secondmethod' cause child* upcast parent* , in turn cause parent's implementation of 'method' called.


Comments

Post a Comment

Popular posts from this blog

Django REST Framework perform_create: You cannot call `.save()` after accessing `serializer.data` -

-
i have following viewset: class artistprofileviewset(viewsets.modelviewset): queryset = artistprofile.objects.all() serializer_class = artistprofileserializer def perform_create(self, serializer): if serializer.is_valid(): serializer.save() with following serializers: class simpleartisttrackserializer(serializers.hyperlinkedmodelserializer): class meta: model = artisttrack fields = (...my fields...) class artistprofileserializer(serializers.hyperlinkedmodelserializer): owners = userserializer(many=true, required=false) tracks = simpleartisttrackserializer(many=true, required=false) class meta: model = artistprofile fields = (...my fields...) i getting following error: assertionerror: cannot call `.save()` after accessing `serializer.data`.if need access data before committing database inspect 'serializer.validated_data' instead. i don't see editing serializer.data object. th...
Read more

Why does Go error when trying to marshal this JSON? -

-
i'm trying rather simple example of trying decode json file structs using golang. however, when attempting error that json: cannot unmarshal object go value of type []main.track which don't understand. here's code in question, , json can found here . package main import ( "encoding/json" "fmt" "net/http" "os" ) // tracks group of track types type tracks struct { tracks []track } // track represents singular track type track struct { name string url string artist artist } // artist represents single artist type artist struct { name string mbid string url string } func main() { url := "http://ws.audioscrobbler.com/2.0/?method=geo.gettoptracks&api_key=c1572082105bd40d247836b5c1819623&format=json&country=netherlands" response, err := http.get(url) if err != nil { fmt.printf("%s\n", err) os.exit(1) } de...
Read more