abstract base class:
#ifndef BUILDINGORG_H
#define BUILDINGORG_H
#include <iostream>
#include <memory>
#include <vector>
class BuildingOrg
{
public:
BuildingOrg(int _id);
virtual int addBuildingComponent(std::shared_ptr<BuildingOrg> buildingOrg,
std::string _type) const;
virtual void removeBuildingComponent(std::shared_ptr<BuildingOrg> buildingOrg);
virtual void getInfo()=0;
private:
int id;
std::string type;
};
#endif // BUILDINGORG_H
concrete subclass:
#ifndef BUILDINGCOMPONENT_H
#define BUILDINGCOMPONENT_H
#include "buildingorg.h"
class BuildingComponent : public BuildingOrg
{
public:
BuildingComponent(int _id);
int addBuildingComponent(std::shared_ptr<BuildingOrg> _buildingOrg,
std::string _type) const override;
void removeBuildingComponent(std::shared_ptr<BuildingOrg> buildingOrg)
override;
void getInfo() override;
private:
std::vector<std::shared_ptr<BuildingOrg>> building_Org;
};
#endif // BUILDINGCOMPONENT_H
Implementation of subclass:
#include "buildingcomponent.h"
BuildingComponent::BuildingComponent(int _id):
BuildingOrg(_id)
{
}
int BuildingComponent::addBuildingComponent(std::shared_ptr<BuildingOrg> _buildingOrg, std::string _type) const
{
building_Org.push_back(_buildingOrg);// I am having error here
return 1;
}
void BuildingComponent::removeBuildingComponent(std::shared_ptr<BuildingOrg> buildingOrg)
{
}
void BuildingComponent::getInfo()
{
}
When I try to put shared pointer in my Vector I get this nasty error;
I really don't know why I am getting the error:
cpp:10: error: passing 'const std::vector<std::shared_ptr<BuildingOrg> >' as 'this' argument of 'void std::vector<_Tp, _Alloc>::push_back(const value_type&) [with _Tp = std::shared_ptr<BuildingOrg>; _Alloc = std::allocator<std::shared_ptr<BuildingOrg> >; std::vector<_Tp, _Alloc>::value_type = std::shared_ptr<BuildingOrg>]' discards qualifiers [-fpermissive]
building_Org.push_back(_buildingOrg);
I don’t understand what is it saying.
The const in int addBuildingComponent(std::shared_ptr<BuildingOrg> _buildingOrg, std::string _type) const override; is a promise that addBuildingComponent will not change BuildingComponent. However, it tries to modify the member variable building_Org with the push_back()...
Removing the const from addBuildingComponent() should fix the error.
The discards qualifiers part of the error message refers to the conflict with the const qualifier of the member function.
C++ template related error messages can be notoriously difficult to parse at first, but it does get easier with practice :-)
You defined BuildingComponent::addBuildingComponent method as const (i.e. that it won't change member varialbles), but you are adding passed in value to a member list (i.e. changing the member variable).
addBuildingComponent() is a const method. within its scope, *this is const, and so this->building_Org is const.
std::vector::push_back() is a non-const method. So it can't be called in a context where the vector is const.
Related
How to add object of class to vector in another class.
#include <iostream>
#include <vector>
#include <string>
using namespace std;
class info{
private:
int id;
string name;
public:
info(int extId, string extName) {
this->id = extId;
this->name = extName;
}
};
class db {
private:
vector<info> infoVector;
public:
void pushData(info * data) {
this->infoVector.push_back(&data);
}
};
int main(){
info * testData = new info(123, "nice");
db database;
database.pushData(testData);
return 0;
}
I am creating a object of info class. The object contains one int and one string variables. Then I am creating db object and I am passing there a testData object.
I got error message while building project.
main.cpp: In member function ‘void db::pushData(info*)’:
main.cpp:23:44: error: no matching function for call to ‘std::vector<info>::push_back(info*&)’
this->infoVector.push_back(data);
^
In file included from /usr/include/c++/5/vector:64:0,
from main.cpp:2:
/usr/include/c++/5/bits/stl_vector.h:913:7: note: candidate: void std::vector<_Tp, _Alloc>::push_back(const value_type&) [with _Tp = info; _Alloc = std::allocator<info>; std::vector<_Tp, _Alloc>::value_type = info]
push_back(const value_type& __x)
^
/usr/include/c++/5/bits/stl_vector.h:913:7: note: no known conversion for argument 1 from ‘info*’ to ‘const value_type& {aka const info&}’
What am I doing wrong?
It looks like you are trying to pass the address of an info * type to vector<info>::push_back, which only accepts types of const info & or info &&. Try using the dereference operator * instead of the address-of operator & when you call push_back:
this->infoVector.push_back(*data);
This isn't a great way to use pointers, however, and could lead to memory leakage or segfaults if data is removed from the vector or if it is deleted. It is better for the vector to own its members, so you might consider doing this instead:
class db {
private:
vector<info> infoVector;
public:
void pushData(info data) { // note: not a pointer
this->infoVector.push_back(data); // note: not address-of
}
};
int main(){
info testData(123, "nice"); // note: not a pointer
db database;
database.pushData(testData);
return 0;
}
Otherwise, if you really want infoVector to contain pointers, declare it as:
std::vector<info*> infoVector;
Then remove the address-to operator.
P.S., avoid using namespace std whenever possible!
You have vector<info> and you want to put info *, try to do:
int main(){
info testData(123, "nice");
db database;
database.pushData(testData);
return 0;
}
I have a Load-Method which builds my unique_ptr (will be more than one later on) and a method to add these unique_ptr to my unordered map. But the code does not compile and I guess it has something to do with scoping...
Here is the code:
#include <unordered_map>
#include <memory>
class MyClass
{
public:
std::string Name;
};
using Map = std::unordered_map<std::string,std::unique_ptr<MyClass>>;
class MyContainer
{
private:
Map myMap;
void AddItem(std::unique_ptr<MyClass> item)
{
myMap.emplace("test", item);
}
public:
void LoadItems()
{
//Read a file ... do something before etc..
std::unique_ptr<MyClass> someItem(new MyClass);
someItem->Name = "FooBar";
AddItem(someItem);
}
};
This is one of the g++ error messages:
error: use of deleted function 'std::unique_ptr<_Tp,
_Dp>::unique_ptr(const std::unique_ptr<_Tp, _Dp>&) [with _Tp = MyClass; _Dp = std::default_delete]'
What is the best way to get this working? I tried changing the signature of the AddItem-method like so:
void AddItem(std::unique_ptr<MyClass>& item) //takes a reference now...
This leads to a real cryptic error message:
In instantiation of 'constexpr std::pair<_T1, _T2>::pair(_U1&&, const
_T2&) [with _U1 = const char (&)[5]; = void; _T1 = const std::basic_string; _T2 = std::unique_ptr]': e:\devtools\winbuilds\include\c++\4.8.3\bits\hashtable_policy.h:177:55:
required from 'std::__detail::_ ...
I suggest trying this piece of code on the fly here, to see the error messages:
http://cpp.sh/
You cannot copy a unique_ptr, because then it will not be unique. You have to move it - AddItem(std::move(someItem)); and myMap.emplace("test", std::move(item));.
You are trying to copy unique_ptr which is not allowed (that constructor is deleted as gcc says in the error). Instead of that you can try with std::move:
#include <unordered_map>
#include <memory>
#include <utility>
class MyClass
{
public:
std::string Name;
};
using Map = std::unordered_map<std::string,std::unique_ptr<MyClass>>;
class MyContainer
{
private:
Map myMap;
void AddItem(std::unique_ptr<MyClass> item)
{
myMap.emplace("test", std::move(item));
}
public:
void LoadItems()
{
//Read a file ... do something before etc..
std::unique_ptr<MyClass> someItem(new MyClass);
someItem->Name = "FooBar";
AddItem(std::move(someItem));
}
};
Be aware, do not use the moved object afterwards.
You can consider to use shared_ptr instead.
Problem
I want to assign values in a class definition which is in a separate header file from the class declaration cpp.
On compilation I recieve theses error messages:
error: ‘const std::map<unsigned int, std::basic_string<char> > bob::mRegexes’ is not a static member of ‘class bob’const std::map<uint,std::string> bob::mRegexes = {
^
error: ‘const std::map<unsigned int, std::basic_string<char> > bob::mResponses’ is not a static member of ‘class bob’ const std::map<uint,std::string> bob::mResponses = {
both of which have been absolutely infurriating because I do not understand why the compiler is ignoring thetypedef for std::string I feel like I'm missing something here but I'm not sure why the bob.h file is seeing the parameters differently than the bob.cpp.
bob.h
#ifndef BOB_H
#define BOB_H
#include <iostream>
#include <string>
#include <boost/regex.hpp>
#include <map>
typedef unsigned int uint;
// This was first to go when I started having problems.
/*using std::string;*/
using std::map;
// boost::regex > c++11::regex (gcc doesn't follow standards).
using boost::regex;
class bob
{
enum respond_to{
QUESTION,
YELL,
NAME,
DEFAULT,
LENGTH
};
public:
static const respond_to mResponseTypes;
static const map<uint,std::string> mRegexes;
static const map<uint,std::string> mResponses;
static std::string hey(std::string sentence);
static const std::string* evaluate (const std::string& sentence);
static const std::string* getResponse(const std::string& sentence, const respond_to& type) noexcept(true);
};
#endif
bob.cpp
#include "bob.h"
const std::map<uint,std::string> bob::mRegexes = {
{QUESTION, "[a-z]+\\?"},
{YELL,"[A-Z]+"}
};
const std::map<uint,std::string> bob::mResponses = {
{QUESTION,"Sure"},
{YELL,"Whoah, chill out!"},
{DEFAULT,"Whatever."}
};
// ...
This might be something really simple but I can't seem to work it out. Within my Vertex I have a std::list<Edge> but when I try to call methods on it like push_front I get an error saying the list is const and I can't push into it. I think for some reason the compiler is converting the std::list<Edge> to a const std::list<Edge>. I know my code isn't set up very well but it's just homework so I'm taking a few shortcuts.
Header file:
#ifndef GRAPH_H
#define GRAPH_H
#include <set>
#include <list>
class Edge{
public:
unsigned int to;
unsigned int weight;
};
class Vertex{
public:
unsigned int id;
std::list<Edge> edges;
bool operator<(const Vertex& other) const{
return id < other.id;
}
};
class Graph{
public:
void add_vertex(unsigned int id);
void add_edge(unsigned int from, unsigned int to, unsigned int weight);
std::set<Vertex> get_vertices();
std::list<Edge> get_edges(unsigned int id);
private:
std::set<Vertex> _vertices;
unsigned int size = 0;
};
Lines causing the error:
void Graph::add_edge(unsigned int from, unsigned int to, unsigned int weight)
{
Vertex find_vert;
find_vert.id = from;
set<Vertex>::iterator from_v = _vertices.find(find_vert);
Edge new_edge;
new_edge.to = to;
new_edge.weight = weight;
from_v->edges.push_front(new_edge); // ERROR HERE
}
Compiler Error message from running g++ -c Graph.cpp:
Graph.cpp:23:38: error: passing ‘const std::list<Edge>’ as ‘this’ argument of ‘void std::list<_Tp,
_Alloc>::push_front(const value_type&) [with _Tp = Edge; _Alloc = std::allocator<Edge>; std::list<_Tp,
_Alloc>::value_type = Edge]’ discards qualifiers [-fpermissive]
The contents of a std::set are implicitly const, because changing the contents could invalidate their sort order.
That makes from_v implicitly const here.
set<Vertex>::iterator from_v = _vertices.find(find_vert);
And your error is telling you that you're trying to modify a const object.
from_v->edges.push_front(new_edge);
// ^^^^^^ const ^^^^^^^^^^ non-const behavior
very simple task for me here and I'm not sure why this is giving me problems, I'm simply making two mockup classes try to compile without any logic in their methods whatsoever using headers and declarations already given to me. Honestly this is just a cut and paste job more than anything, and yet I still came across this golden nugget of love -
cbutton.cpp:11:44: error: default argument given for parameter 4 of ‘cio::CButton::CButton(const char*, int, int, bool, const char*)’ [-fpermissive]
cbutton.h:7:5: error: after previous specification in ‘cio::CButton::CButton(const char*, int, int, bool, const char*)’ [-fpermissive]
cbutton.cpp:11:44: error: default argument given for parameter 5 of ‘cio::CButton::CButton(const char*, int, int, bool, const char*)’ [-fpermissive]
cbutton.h:7:5: error: after previous specification in ‘cio::CButton::CButton(const char*, int, int, bool, const char*)’ [-fpermissive]
cbutton.cpp:19:41: error: default argument given for parameter 1 of ‘void cio::CButton::draw(int)’ [-fpermissive]
cbutton.h:11:10: error: after previous specification in ‘virtual void cio::CButton::draw(int)’ [-fpermissive]
cbutton.cpp:53:29: error: ‘virtual’ outside class declaration
Here are the files I'm working with. Thank you everyone, as always!
#include "cfield.h"
namespace cio{
class CButton: public CField{
public:
CButton(const char *Str, int Row, int Col,
bool Bordered = true,
const char* Border=C_BORDER_CHARS);
virtual ~CButton();
void draw(int rn=C_FULL_FRAME);
int edit();
bool editable()const;
void set(const void* str);
};
}
#include "cbutton.h"
namespace cio {
CButton::CButton(const char *Str, int Row, int Col,
bool Bordered = true,
const char* Border=C_BORDER_CHARS){
}
void CButton::draw(int rn=C_FULL_FRAME){
}
int CButton::edit(){
return 0;
}
bool CButton::editable()const {
return false;
}
void CButton::set(const void* str){
}
virtual CButton::~CButton(){
}
}
You specified a default argument in the definition of the function, while they already had a default argument in the class declaration. You can declare default arguments in the class declaration or in the function definition, but not both.
EDIT: Missed the end of your errors: error: ‘virtual’ outside class declaration. It's a rather clear compiler error: virtual keywords belongs to class declarations, not function definitions. Simply remove it from the definition of your destructor.
Corrected source:
namespace cio {
CButton::CButton(const char *Str, int Row, int Col,
bool Bordered, // No default parameter here,
const char* Border){ // here,
}
void CButton::draw(int rn){ // and here
}
CButton::~CButton(){ // No virtual keyword here
}
}
You're not allowed to repeat default arguments when you define a function. They belong only on the declaration. (The actual rule isn't quite that simple, because a definition can also be a definition, but you get the idea...)
You dont include the default parameter in your function definition, the prototype is the only one you need to include the default value into.
#include "cbutton.h"
namespace cio {
CButton::CButton(const char *Str, int Row, int Col,
bool Bordered,
const char* Border){ //remove in def
}
void CButton::draw(int rn){
}