error: no matching function for call to 'std::reference_wrapper::reference

error: no matching function for call to 'std::reference_wrapper::reference_wrapper()

-2

Book and Article are derived classes from Medium.

Why am I getting this error when trying to insert Medium / Book / Article in the bibliography?

error: no matching function for call to '**std::reference_wrapper<Medium>::reference_wrapper()**

Compiler error

main.cc

#include <iostream>

using namespace std;

#include "Bibliography.h"

#include "Medium.h"

#include "Book.h"

#include "Article.h"



int main()

{

    Bibliography p(1);

    Medium m1("PN","I","Pasol nah",2017);

    p.insert(m1);

    cout << p;

    return 0;

}

Bibliography.h

#ifndef BIBLIOGRAPHY_H_

#define BIBLIOGRAPHY_H_



#include "Medium.h"

#include "Article.h"

#include "Book.h"

#include <iostream>

#include <functional>

#include <vector>



class Bibliography

{

  private:

    int m_Size;

    std::vector<std::reference_wrapper<Medium>> v;

    int index;

  public:

    Bibliography(int size);

    void insert(Medium m);

    friend std::ostream& operator<<(std::ostream& out, const Bibliography &b1);

};



#endif

Bibliography.cc

#include "Bibliography.h"



Bibliography::Bibliography(int size)

{

    std::cout << "Bibliography created n";

    m_Size = size;

    v.resize(m_Size);

    index = 0;

}



void Bibliography::insert(Medium m)

{

    v.push_back(m);

}



std::ostream& operator<<(std::ostream& out, const Bibliography &b1)

{

    for (Medium &Medium : b1.v)

    {

        out << Medium.toString() << std::endl;

    }

    return out;

}

edited Nov 25 '18 at 15:03

vallismortis

3,621104265

asked Dec 16 '17 at 19:16

Gicu Mironica

add a comment |

-2

Book and Article are derived classes from Medium.

Why am I getting this error when trying to insert Medium / Book / Article in the bibliography?

error: no matching function for call to '**std::reference_wrapper<Medium>::reference_wrapper()**

Compiler error

main.cc

#include <iostream>

using namespace std;

#include "Bibliography.h"

#include "Medium.h"

#include "Book.h"

#include "Article.h"



int main()

{

    Bibliography p(1);

    Medium m1("PN","I","Pasol nah",2017);

    p.insert(m1);

    cout << p;

    return 0;

}

Bibliography.h

#ifndef BIBLIOGRAPHY_H_

#define BIBLIOGRAPHY_H_



#include "Medium.h"

#include "Article.h"

#include "Book.h"

#include <iostream>

#include <functional>

#include <vector>



class Bibliography

{

  private:

    int m_Size;

    std::vector<std::reference_wrapper<Medium>> v;

    int index;

  public:

    Bibliography(int size);

    void insert(Medium m);

    friend std::ostream& operator<<(std::ostream& out, const Bibliography &b1);

};



#endif

Bibliography.cc

#include "Bibliography.h"



Bibliography::Bibliography(int size)

{

    std::cout << "Bibliography created n";

    m_Size = size;

    v.resize(m_Size);

    index = 0;

}



void Bibliography::insert(Medium m)

{

    v.push_back(m);

}



std::ostream& operator<<(std::ostream& out, const Bibliography &b1)

{

    for (Medium &Medium : b1.v)

    {

        out << Medium.toString() << std::endl;

    }

    return out;

}

edited Nov 25 '18 at 15:03

vallismortis

3,621104265

asked Dec 16 '17 at 19:16

Gicu Mironica

add a comment |

-2

Book and Article are derived classes from Medium.

Why am I getting this error when trying to insert Medium / Book / Article in the bibliography?

error: no matching function for call to '**std::reference_wrapper<Medium>::reference_wrapper()**

Compiler error

main.cc

#include <iostream>

using namespace std;

#include "Bibliography.h"

#include "Medium.h"

#include "Book.h"

#include "Article.h"



int main()

{

    Bibliography p(1);

    Medium m1("PN","I","Pasol nah",2017);

    p.insert(m1);

    cout << p;

    return 0;

}

Bibliography.h

#ifndef BIBLIOGRAPHY_H_

#define BIBLIOGRAPHY_H_



#include "Medium.h"

#include "Article.h"

#include "Book.h"

#include <iostream>

#include <functional>

#include <vector>



class Bibliography

{

  private:

    int m_Size;

    std::vector<std::reference_wrapper<Medium>> v;

    int index;

  public:

    Bibliography(int size);

    void insert(Medium m);

    friend std::ostream& operator<<(std::ostream& out, const Bibliography &b1);

};



#endif

Bibliography.cc

#include "Bibliography.h"



Bibliography::Bibliography(int size)

{

    std::cout << "Bibliography created n";

    m_Size = size;

    v.resize(m_Size);

    index = 0;

}



void Bibliography::insert(Medium m)

{

    v.push_back(m);

}



std::ostream& operator<<(std::ostream& out, const Bibliography &b1)

{

    for (Medium &Medium : b1.v)

    {

        out << Medium.toString() << std::endl;

    }

    return out;

}

edited Nov 25 '18 at 15:03

vallismortis

3,621104265

asked Dec 16 '17 at 19:16

Gicu Mironica

Book and Article are derived classes from Medium.

Why am I getting this error when trying to insert Medium / Book / Article in the bibliography?

error: no matching function for call to '**std::reference_wrapper<Medium>::reference_wrapper()**

Compiler error

main.cc

#include <iostream>

using namespace std;

#include "Bibliography.h"

#include "Medium.h"

#include "Book.h"

#include "Article.h"



int main()

{

    Bibliography p(1);

    Medium m1("PN","I","Pasol nah",2017);

    p.insert(m1);

    cout << p;

    return 0;

}

Bibliography.h

#ifndef BIBLIOGRAPHY_H_

#define BIBLIOGRAPHY_H_



#include "Medium.h"

#include "Article.h"

#include "Book.h"

#include <iostream>

#include <functional>

#include <vector>



class Bibliography

{

  private:

    int m_Size;

    std::vector<std::reference_wrapper<Medium>> v;

    int index;

  public:

    Bibliography(int size);

    void insert(Medium m);

    friend std::ostream& operator<<(std::ostream& out, const Bibliography &b1);

};



#endif

Bibliography.cc

#include "Bibliography.h"



Bibliography::Bibliography(int size)

{

    std::cout << "Bibliography created n";

    m_Size = size;

    v.resize(m_Size);

    index = 0;

}



void Bibliography::insert(Medium m)

{

    v.push_back(m);

}



std::ostream& operator<<(std::ostream& out, const Bibliography &b1)

{

    for (Medium &Medium : b1.v)

    {

        out << Medium.toString() << std::endl;

    }

    return out;

}

c++ stdvector reference-wrapper

edited Nov 25 '18 at 15:03

vallismortis

3,621104265

asked Dec 16 '17 at 19:16

Gicu Mironica

edited Nov 25 '18 at 15:03

vallismortis

3,621104265

asked Dec 16 '17 at 19:16

Gicu Mironica

edited Nov 25 '18 at 15:03

vallismortis

3,621104265

edited Nov 25 '18 at 15:03

vallismortis

3,621104265

edited Nov 25 '18 at 15:03

vallismortis

3,621104265

asked Dec 16 '17 at 19:16

Gicu Mironica

asked Dec 16 '17 at 19:16

Gicu Mironica

asked Dec 16 '17 at 19:16

Gicu Mironica

add a comment |

1 Answer
1

active

oldest

votes

You should not use reference_wrapper in vector, because vector can keep objects which have default constructor, reference_wrapper doesn't have it, look at these constructors of reference_wrapper:

initialization (1)  

reference_wrapper (type& ref) noexcept;

reference_wrapper (type&&) = delete;

copy (2)    

reference_wrapper (const reference_wrapper& x) noexcept;

In this line

v.resize(m_Size);

you want to create m_Size reference_wrapperobjects, but default constructor for reference_wrapper doesn't exist, and code cannot be compiled.

You can use reference_wrapper with vector but you get compilation error
when method of vector is called which needs default constructor to be defined.

edited Dec 16 '17 at 20:43

answered Dec 16 '17 at 19:39

rafix07

7,9381714

Is this really true? The C++ Reference specifically uses a vector as the example usage of a reference_wrapper.

– vallismortis
Nov 25 '18 at 14:23

1

In the example you posted there is a list with 10 elements. list<int> l(10); vector keeps reference_wrapper<int>, when this vector is created v(l.begin(),l.end()) constructor of reference_wrapper is called which takes Lvalues as parameter, storing pointer to these Lvalues, so in this case vector+reference_wrapper works. But resize on vector cannot be called because resize calls default ctor for reference_wrapper. reference_wrapper needs to store pointer to some object (reference needs to be initialized). Therefore default ctor for reference_wrapper doesn't exist.

– rafix07
Nov 25 '18 at 14:43

Much appreciated. The C++ Reference would be more helpful if it included examples like this.

– vallismortis
Nov 25 '18 at 15:00

add a comment |

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1 Answer
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1 Answer
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initialization (1)  

reference_wrapper (type& ref) noexcept;

reference_wrapper (type&&) = delete;

copy (2)    

reference_wrapper (const reference_wrapper& x) noexcept;

In this line

v.resize(m_Size);

you want to create m_Size reference_wrapperobjects, but default constructor for reference_wrapper doesn't exist, and code cannot be compiled.

You can use reference_wrapper with vector but you get compilation error
when method of vector is called which needs default constructor to be defined.

edited Dec 16 '17 at 20:43

answered Dec 16 '17 at 19:39

rafix07

7,9381714

Is this really true? The C++ Reference specifically uses a vector as the example usage of a reference_wrapper.

– vallismortis
Nov 25 '18 at 14:23

1

In the example you posted there is a list with 10 elements. list<int> l(10); vector keeps reference_wrapper<int>, when this vector is created v(l.begin(),l.end()) constructor of reference_wrapper is called which takes Lvalues as parameter, storing pointer to these Lvalues, so in this case vector+reference_wrapper works. But resize on vector cannot be called because resize calls default ctor for reference_wrapper. reference_wrapper needs to store pointer to some object (reference needs to be initialized). Therefore default ctor for reference_wrapper doesn't exist.

– rafix07
Nov 25 '18 at 14:43

Much appreciated. The C++ Reference would be more helpful if it included examples like this.

– vallismortis
Nov 25 '18 at 15:00

add a comment |

initialization (1)  

reference_wrapper (type& ref) noexcept;

reference_wrapper (type&&) = delete;

copy (2)    

reference_wrapper (const reference_wrapper& x) noexcept;

In this line

v.resize(m_Size);

you want to create m_Size reference_wrapperobjects, but default constructor for reference_wrapper doesn't exist, and code cannot be compiled.

You can use reference_wrapper with vector but you get compilation error
when method of vector is called which needs default constructor to be defined.

edited Dec 16 '17 at 20:43

answered Dec 16 '17 at 19:39

rafix07

7,9381714

Is this really true? The C++ Reference specifically uses a vector as the example usage of a reference_wrapper.

– vallismortis
Nov 25 '18 at 14:23

1

In the example you posted there is a list with 10 elements. list<int> l(10); vector keeps reference_wrapper<int>, when this vector is created v(l.begin(),l.end()) constructor of reference_wrapper is called which takes Lvalues as parameter, storing pointer to these Lvalues, so in this case vector+reference_wrapper works. But resize on vector cannot be called because resize calls default ctor for reference_wrapper. reference_wrapper needs to store pointer to some object (reference needs to be initialized). Therefore default ctor for reference_wrapper doesn't exist.

– rafix07
Nov 25 '18 at 14:43

Much appreciated. The C++ Reference would be more helpful if it included examples like this.

– vallismortis
Nov 25 '18 at 15:00

add a comment |

initialization (1)  

reference_wrapper (type& ref) noexcept;

reference_wrapper (type&&) = delete;

copy (2)    

reference_wrapper (const reference_wrapper& x) noexcept;

In this line

v.resize(m_Size);

you want to create m_Size reference_wrapperobjects, but default constructor for reference_wrapper doesn't exist, and code cannot be compiled.

You can use reference_wrapper with vector but you get compilation error
when method of vector is called which needs default constructor to be defined.

edited Dec 16 '17 at 20:43

answered Dec 16 '17 at 19:39

rafix07

7,9381714

initialization (1)  

reference_wrapper (type& ref) noexcept;

reference_wrapper (type&&) = delete;

copy (2)    

reference_wrapper (const reference_wrapper& x) noexcept;

In this line

v.resize(m_Size);

you want to create m_Size reference_wrapperobjects, but default constructor for reference_wrapper doesn't exist, and code cannot be compiled.

You can use reference_wrapper with vector but you get compilation error
when method of vector is called which needs default constructor to be defined.

edited Dec 16 '17 at 20:43

answered Dec 16 '17 at 19:39

rafix07

7,9381714

edited Dec 16 '17 at 20:43

answered Dec 16 '17 at 19:39

rafix07

7,9381714

answered Dec 16 '17 at 19:39

rafix07

7,9381714

answered Dec 16 '17 at 19:39

rafix07

7,9381714

Is this really true? The C++ Reference specifically uses a vector as the example usage of a reference_wrapper.

– vallismortis
Nov 25 '18 at 14:23

1

In the example you posted there is a list with 10 elements. list<int> l(10); vector keeps reference_wrapper<int>, when this vector is created v(l.begin(),l.end()) constructor of reference_wrapper is called which takes Lvalues as parameter, storing pointer to these Lvalues, so in this case vector+reference_wrapper works. But resize on vector cannot be called because resize calls default ctor for reference_wrapper. reference_wrapper needs to store pointer to some object (reference needs to be initialized). Therefore default ctor for reference_wrapper doesn't exist.

– rafix07
Nov 25 '18 at 14:43

Much appreciated. The C++ Reference would be more helpful if it included examples like this.

– vallismortis
Nov 25 '18 at 15:00

add a comment |

Is this really true? The C++ Reference specifically uses a vector as the example usage of a reference_wrapper.

– vallismortis
Nov 25 '18 at 14:23

1

In the example you posted there is a list with 10 elements. list<int> l(10); vector keeps reference_wrapper<int>, when this vector is created v(l.begin(),l.end()) constructor of reference_wrapper is called which takes Lvalues as parameter, storing pointer to these Lvalues, so in this case vector+reference_wrapper works. But resize on vector cannot be called because resize calls default ctor for reference_wrapper. reference_wrapper needs to store pointer to some object (reference needs to be initialized). Therefore default ctor for reference_wrapper doesn't exist.

– rafix07
Nov 25 '18 at 14:43

Much appreciated. The C++ Reference would be more helpful if it included examples like this.

– vallismortis
Nov 25 '18 at 15:00

Is this really true? The C++ Reference specifically uses a vector as the example usage of a reference_wrapper.

– vallismortis
Nov 25 '18 at 14:23

In the example you posted there is a list with 10 elements. list<int> l(10); vector keeps reference_wrapper<int>, when this vector is created v(l.begin(),l.end()) constructor of reference_wrapper is called which takes Lvalues as parameter, storing pointer to these Lvalues, so in this case vector+reference_wrapper works. But resize on vector cannot be called because resize calls default ctor for reference_wrapper. reference_wrapper needs to store pointer to some object (reference needs to be initialized). Therefore default ctor for reference_wrapper doesn't exist.

– rafix07
Nov 25 '18 at 14:43

Much appreciated. The C++ Reference would be more helpful if it included examples like this.

– vallismortis
Nov 25 '18 at 15:00

add a comment |

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