Unordered_map gets empty after inserting an element, what am I doing wrong?
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I have an unordered_map object, which I fill somewhere, and when look for what I put, the map is empty.
I have a ClassA-object which has a ClassB private member. ClassB has a private member of ClassC* and an unordered_map<std::string, ClassC*> private member. It also has public functions insertClassC(std::string name, ClassC* o) and setActiveClassC(std::string name). My main()-function, has a ClassC object, calls insertClassC(), and then calls setActiveClassC().
int main()
{
ClassC mainClassC;
try
{
ClassA app;
app.getClassB().insertClassC("main", &mainClassC);
app.getClassB().setActiveClassC("main");
} catch (const std::exception& e)
{
std::cerr << e.what() << std::endl;
return EXIT_FAILURE;
}
return EXIT_SUCCESS;
}
ClassB ClassA::getClassB()
{
return classBObject; // private member of ClassA
}
void ClassB::insertClassC(std::string name, ClassC* o)
{
// classCMap is an unordered_map<std::string, ClassC*>, private member of ClassB
classCMap.insert(std::pair<std::string, ClassC*> (name, o));
}
void ClassB::setActiveClassC(const std::string name)
{
std::unordered_map<std::string, ClassC*>::const_iterator res = classCMap.find(name);
if(res == classCMap.end())
{
char err [50];
sprintf(err, "ClassC "%s" could not be found", name.c_str());
throw std::runtime_error(err);
}
active = res->second;
}
I would expect this program to return EXIT_SUCCESS, but it returns EXIT_FAILURE and prints to stderr:
ClassC "main" could not be found
When debugging, I can see that the size of classCMap is 1 at the end of the insertClassC() call, but it's 0 when I call setActiveClassC().
I suspect my understanding of pointers is wrong (I'm kind of a beginner with c++), so I read stuff about that, but I still don't understand my mistake.
c++
asked Dec 22 '18 at 9:09
aTomaTom
398
add a comment |
I have an unordered_map object, which I fill somewhere, and when look for what I put, the map is empty.
I have a ClassA-object which has a ClassB private member. ClassB has a private member of ClassC* and an unordered_map<std::string, ClassC*> private member. It also has public functions insertClassC(std::string name, ClassC* o) and setActiveClassC(std::string name). My main()-function, has a ClassC object, calls insertClassC(), and then calls setActiveClassC().
int main()
{
ClassC mainClassC;
try
{
ClassA app;
app.getClassB().insertClassC("main", &mainClassC);
app.getClassB().setActiveClassC("main");
} catch (const std::exception& e)
{
std::cerr << e.what() << std::endl;
return EXIT_FAILURE;
}
return EXIT_SUCCESS;
}
ClassB ClassA::getClassB()
{
return classBObject; // private member of ClassA
}
void ClassB::insertClassC(std::string name, ClassC* o)
{
// classCMap is an unordered_map<std::string, ClassC*>, private member of ClassB
classCMap.insert(std::pair<std::string, ClassC*> (name, o));
}
void ClassB::setActiveClassC(const std::string name)
{
std::unordered_map<std::string, ClassC*>::const_iterator res = classCMap.find(name);
if(res == classCMap.end())
{
char err [50];
sprintf(err, "ClassC "%s" could not be found", name.c_str());
throw std::runtime_error(err);
}
active = res->second;
}
I would expect this program to return EXIT_SUCCESS, but it returns EXIT_FAILURE and prints to stderr:
ClassC "main" could not be found
When debugging, I can see that the size of classCMap is 1 at the end of the insertClassC() call, but it's 0 when I call setActiveClassC().
I suspect my understanding of pointers is wrong (I'm kind of a beginner with c++), so I read stuff about that, but I still don't understand my mistake.
c++
asked Dec 22 '18 at 9:09
aTomaTom
398
1
app.getClassB()returns a copy of your private class member. Try changing the signature ofgetClassBtoClassB& getClassB()and then it should do something.
– Thomas Lang
Dec 22 '18 at 9:16
add a comment |
I have an unordered_map object, which I fill somewhere, and when look for what I put, the map is empty.
I have a ClassA-object which has a ClassB private member. ClassB has a private member of ClassC* and an unordered_map<std::string, ClassC*> private member. It also has public functions insertClassC(std::string name, ClassC* o) and setActiveClassC(std::string name). My main()-function, has a ClassC object, calls insertClassC(), and then calls setActiveClassC().
int main()
{
ClassC mainClassC;
try
{
ClassA app;
app.getClassB().insertClassC("main", &mainClassC);
app.getClassB().setActiveClassC("main");
} catch (const std::exception& e)
{
std::cerr << e.what() << std::endl;
return EXIT_FAILURE;
}
return EXIT_SUCCESS;
}
ClassB ClassA::getClassB()
{
return classBObject; // private member of ClassA
}
void ClassB::insertClassC(std::string name, ClassC* o)
{
// classCMap is an unordered_map<std::string, ClassC*>, private member of ClassB
classCMap.insert(std::pair<std::string, ClassC*> (name, o));
}
void ClassB::setActiveClassC(const std::string name)
{
std::unordered_map<std::string, ClassC*>::const_iterator res = classCMap.find(name);
if(res == classCMap.end())
{
char err [50];
sprintf(err, "ClassC "%s" could not be found", name.c_str());
throw std::runtime_error(err);
}
active = res->second;
}
I would expect this program to return EXIT_SUCCESS, but it returns EXIT_FAILURE and prints to stderr:
ClassC "main" could not be found
When debugging, I can see that the size of classCMap is 1 at the end of the insertClassC() call, but it's 0 when I call setActiveClassC().
I suspect my understanding of pointers is wrong (I'm kind of a beginner with c++), so I read stuff about that, but I still don't understand my mistake.
c++
asked Dec 22 '18 at 9:09
aTomaTom
398
I have an unordered_map object, which I fill somewhere, and when look for what I put, the map is empty.
I have a ClassA-object which has a ClassB private member. ClassB has a private member of ClassC* and an unordered_map<std::string, ClassC*> private member. It also has public functions insertClassC(std::string name, ClassC* o) and setActiveClassC(std::string name). My main()-function, has a ClassC object, calls insertClassC(), and then calls setActiveClassC().
int main()
{
ClassC mainClassC;
try
{
ClassA app;
app.getClassB().insertClassC("main", &mainClassC);
app.getClassB().setActiveClassC("main");
} catch (const std::exception& e)
{
std::cerr << e.what() << std::endl;
return EXIT_FAILURE;
}
return EXIT_SUCCESS;
}
ClassB ClassA::getClassB()
{
return classBObject; // private member of ClassA
}
void ClassB::insertClassC(std::string name, ClassC* o)
{
// classCMap is an unordered_map<std::string, ClassC*>, private member of ClassB
classCMap.insert(std::pair<std::string, ClassC*> (name, o));
}
void ClassB::setActiveClassC(const std::string name)
{
std::unordered_map<std::string, ClassC*>::const_iterator res = classCMap.find(name);
if(res == classCMap.end())
{
char err [50];
sprintf(err, "ClassC "%s" could not be found", name.c_str());
throw std::runtime_error(err);
}
active = res->second;
}
I would expect this program to return EXIT_SUCCESS, but it returns EXIT_FAILURE and prints to stderr:
ClassC "main" could not be found
When debugging, I can see that the size of classCMap is 1 at the end of the insertClassC() call, but it's 0 when I call setActiveClassC().
I suspect my understanding of pointers is wrong (I'm kind of a beginner with c++), so I read stuff about that, but I still don't understand my mistake.
c++
c++
asked Dec 22 '18 at 9:09
aTomaTom
398
asked Dec 22 '18 at 9:09
aTomaTom
398
edited Jan 4 at 6:20
aTom
asked Dec 22 '18 at 9:09
aTomaTom
398
asked Dec 22 '18 at 9:09
aTomaTom
398
asked Dec 22 '18 at 9:09
aTomaTom
398
398
1
app.getClassB()returns a copy of your private class member. Try changing the signature ofgetClassBtoClassB& getClassB()and then it should do something.
– Thomas Lang
Dec 22 '18 at 9:16
add a comment |
1
app.getClassB()returns a copy of your private class member. Try changing the signature ofgetClassBtoClassB& getClassB()and then it should do something.
– Thomas Lang
Dec 22 '18 at 9:16
1
1
app.getClassB() returns a copy of your private class member. Try changing the signature of getClassB to ClassB& getClassB() and then it should do something.– Thomas Lang
Dec 22 '18 at 9:16
app.getClassB() returns a copy of your private class member. Try changing the signature of getClassB to ClassB& getClassB() and then it should do something.– Thomas Lang
Dec 22 '18 at 9:16
add a comment |
1 Answer
1
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oldest
votes
Okay, so I decided to make my comment an answer:
Your function
ClassB ClassA::getClassB()
{
return classBObject; // private member of ClassA
}
has return type ClassB which means it copies your private member.
But since you want to modify your member, you need to return a reference to your member, i.e. you'd have to write
ClassB& ClassA::getClassB()
{
return classBObject; // private member of ClassA
}
Note the ampersand on the return type.
answered Dec 22 '18 at 9:18
Thomas LangThomas Lang
555311
add a comment |
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Okay, so I decided to make my comment an answer:
Your function
ClassB ClassA::getClassB()
{
return classBObject; // private member of ClassA
}
has return type ClassB which means it copies your private member.
But since you want to modify your member, you need to return a reference to your member, i.e. you'd have to write
ClassB& ClassA::getClassB()
{
return classBObject; // private member of ClassA
}
Note the ampersand on the return type.
answered Dec 22 '18 at 9:18
Thomas LangThomas Lang
555311
add a comment |
Okay, so I decided to make my comment an answer:
Your function
ClassB ClassA::getClassB()
{
return classBObject; // private member of ClassA
}
has return type ClassB which means it copies your private member.
But since you want to modify your member, you need to return a reference to your member, i.e. you'd have to write
ClassB& ClassA::getClassB()
{
return classBObject; // private member of ClassA
}
Note the ampersand on the return type.
answered Dec 22 '18 at 9:18
Thomas LangThomas Lang
555311
add a comment |
Okay, so I decided to make my comment an answer:
Your function
ClassB ClassA::getClassB()
{
return classBObject; // private member of ClassA
}
has return type ClassB which means it copies your private member.
But since you want to modify your member, you need to return a reference to your member, i.e. you'd have to write
ClassB& ClassA::getClassB()
{
return classBObject; // private member of ClassA
}
Note the ampersand on the return type.
answered Dec 22 '18 at 9:18
Thomas LangThomas Lang
555311
Okay, so I decided to make my comment an answer:
Your function
ClassB ClassA::getClassB()
{
return classBObject; // private member of ClassA
}
has return type ClassB which means it copies your private member.
But since you want to modify your member, you need to return a reference to your member, i.e. you'd have to write
ClassB& ClassA::getClassB()
{
return classBObject; // private member of ClassA
}
Note the ampersand on the return type.
answered Dec 22 '18 at 9:18
Thomas LangThomas Lang
555311
answered Dec 22 '18 at 9:18
Thomas LangThomas Lang
555311
answered Dec 22 '18 at 9:18
Thomas LangThomas Lang
555311
answered Dec 22 '18 at 9:18
Thomas LangThomas Lang
555311
555311
add a comment |
add a comment |
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app.getClassB()returns a copy of your private class member. Try changing the signature ofgetClassBtoClassB& getClassB()and then it should do something.– Thomas Lang
Dec 22 '18 at 9:16