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keine Übereinstimmung für ´ operator << ’in ″ std :: operator

Ich bin ein C++ - Neuling. Ich habe mein erstes Programm hier ausprobiert. In meinen Augen ist dieses Programm korrekt.

#include <iostream>

using namespace std;

class mystruct
{
    private:
        int m_a;
        float m_b;

    public:
        mystruct(int x, float y)
        {
                m_a = x;
                m_b = y;
        }

};


int main()
{

        mystruct m = mystruct(5,3.14);

        cout << "my structure " << m << endl;

        return 0;
}

Ich bekomme jedoch so viele Fehler. Kann nicht herausfinden warum?

cout.cpp: In function ‘int main()’:
cout.cpp:26:29: error: no match for ‘operator<<’ in ‘std::operator<< [with _Traits = std::char_traits<char>]((* & std::cout), ((const char*)"my structure ")) << m’
cout.cpp:26:29: note: candidates are:
/usr/include/c++/4.6/ostream:110:7: note: std::basic_ostream<_CharT, _Traits>::__ostream_type& std::basic_ostream<_CharT, _Traits>::operator<<(std::basic_ostream<_CharT, _Traits>::__ostream_type& (*)(std::basic_ostream<_CharT, _Traits>::__ostream_type&)) [with _CharT = char, _Traits = std::char_traits<char>, std::basic_ostream<_CharT, _Traits>::__ostream_type = std::basic_ostream<char>]
/usr/include/c++/4.6/ostream:110:7: note:   no known conversion for argument 1 from ‘mystruct’ to ‘std::basic_ostream<char>::__ostream_type& (*)(std::basic_ostream<char>::__ostream_type&) {aka std::basic_ostream<char>& (*)(std::basic_ostream<char>&)}’
/usr/include/c++/4.6/ostream:119:7: note: std::basic_ostream<_CharT, _Traits>::__ostream_type& std::basic_ostream<_CharT, _Traits>::operator<<(std::basic_ostream<_CharT, _Traits>::__ios_type& (*)(std::basic_ostream<_CharT, _Traits>::__ios_type&)) [with _CharT = char, _Traits = std::char_traits<char>, std::basic_ostream<_CharT, _Traits>::__ostream_type = std::basic_ostream<char>, std::basic_ostream<_CharT, _Traits>::__ios_type = std::basic_ios<char>]
/usr/include/c++/4.6/ostream:119:7: note:   no known conversion for argument 1 from ‘mystruct’ to ‘std::basic_ostream<char>::__ios_type& (*)(std::basic_ostream<char>::__ios_type&) {aka std::basic_ios<char>& (*)(std::basic_ios<char>&)}’
/usr/include/c++/4.6/ostream:129:7: note: std::basic_ostream<_CharT, _Traits>::__ostream_type& std::basic_ostream<_CharT, _Traits>::operator<<(std::ios_base& (*)(std::ios_base&)) [with _CharT = char, _Traits = std::char_traits<char>, std::basic_ostream<_CharT, _Traits>::__ostream_type = std::basic_ostream<char>]
/usr/include/c++/4.6/ostream:129:7: note:   no known conversion for argument 1 from ‘mystruct’ to ‘std::ios_base& (*)(std::ios_base&)’
/usr/include/c++/4.6/ostream:167:7: note: std::basic_ostream<_CharT, _Traits>::__ostream_type& std::basic_ostream<_CharT, _Traits>::operator<<(long int) [with _CharT = char, _Traits = std::char_traits<char>, std::basic_ostream<_CharT, _Traits>::__ostream_type = std::basic_ostream<char>]
/usr/include/c++/4.6/ostream:167:7: note:   no known conversion for argument 1 from ‘mystruct’ to ‘long int’
/usr/include/c++/4.6/ostream:171:7: note: std::basic_ostream<_CharT, _Traits>::__ostream_type& std::basic_ostream<_CharT, _Traits>::operator<<(long unsigned int) [with _CharT = char, _Traits = std::char_traits<char>, std::basic_ostream<_CharT, _Traits>::__ostream_type = std::basic_ostream<char>]
/usr/include/c++/4.6/ostream:171:7: note:   no known conversion for argument 1 from ‘mystruct’ to ‘long unsigned int’
/usr/include/c++/4.6/ostream:175:7: note: std::basic_ostream<_CharT, _Traits>::__ostream_type& std::basic_ostream<_CharT, _Traits>::operator<<(bool) [with _CharT = char, _Traits = std::char_traits<char>, std::basic_ostream<_CharT, _Traits>::__ostream_type = std::basic_ostream<char>]
/usr/include/c++/4.6/ostream:175:7: note:   no known conversion for argument 1 from ‘mystruct’ to ‘bool’
/usr/include/c++/4.6/bits/ostream.tcc:93:5: note: std::basic_ostream<_CharT, _Traits>& std::basic_ostream<_CharT, _Traits>::operator<<(short int) [with _CharT = char, _Traits = std::char_traits<char>]
/usr/include/c++/4.6/bits/ostream.tcc:93:5: note:   no known conversion for argument 1 from ‘mystruct’ to ‘short int’
/usr/include/c++/4.6/ostream:182:7: note: std::basic_ostream<_CharT, _Traits>::__ostream_type& std::basic_ostream<_CharT, _Traits>::operator<<(short unsigned int) [with _CharT = char, _Traits = std::char_traits<char>, std::basic_ostream<_CharT, _Traits>::__ostream_type = std::basic_ostream<char>]
/usr/include/c++/4.6/ostream:182:7: note:   no known conversion for argument 1 from ‘mystruct’ to ‘short unsigned int’
/usr/include/c++/4.6/bits/ostream.tcc:107:5: note: std::basic_ostream<_CharT, _Traits>& std::basic_ostream<_CharT, _Traits>::operator<<(int) [with _CharT = char, _Traits = std::char_traits<char>]
/usr/include/c++/4.6/bits/ostream.tcc:107:5: note:   no known conversion for argument 1 from ‘mystruct’ to ‘int’
/usr/include/c++/4.6/ostream:193:7: note: std::basic_ostream<_CharT, _Traits>::__ostream_type& std::basic_ostream<_CharT, _Traits>::operator<<(unsigned int) [with _CharT = char, _Traits = std::char_traits<char>, std::basic_ostream<_CharT, _Traits>::__ostream_type = std::basic_ostream<char>]
/usr/include/c++/4.6/ostream:193:7: note:   no known conversion for argument 1 from ‘mystruct’ to ‘unsigned int’
/usr/include/c++/4.6/ostream:202:7: note: std::basic_ostream<_CharT, _Traits>::__ostream_type& std::basic_ostream<_CharT, _Traits>::operator<<(long long int) [with _CharT = char, _Traits = std::char_traits<char>, std::basic_ostream<_CharT, _Traits>::__ostream_type = std::basic_ostream<char>]
/usr/include/c++/4.6/ostream:202:7: note:   no known conversion for argument 1 from ‘mystruct’ to ‘long long int’
/usr/include/c++/4.6/ostream:206:7: note: std::basic_ostream<_CharT, _Traits>::__ostream_type& std::basic_ostream<_CharT, _Traits>::operator<<(long long unsigned int) [with _CharT = char, _Traits = std::char_traits<char>, std::basic_ostream<_CharT, _Traits>::__ostream_type = std::basic_ostream<char>]
/usr/include/c++/4.6/ostream:206:7: note:   no known conversion for argument 1 from ‘mystruct’ to ‘long long unsigned int’
/usr/include/c++/4.6/ostream:211:7: note: std::basic_ostream<_CharT, _Traits>::__ostream_type& std::basic_ostream<_CharT, _Traits>::operator<<(double) [with _CharT = char, _Traits = std::char_traits<char>, std::basic_ostream<_CharT, _Traits>::__ostream_type = std::basic_ostream<char>]
/usr/include/c++/4.6/ostream:211:7: note:   no known conversion for argument 1 from ‘mystruct’ to ‘double’
/usr/include/c++/4.6/ostream:215:7: note: std::basic_ostream<_CharT, _Traits>::__ostream_type& std::basic_ostream<_CharT, _Traits>::operator<<(float) [with _CharT = char, _Traits = std::char_traits<char>, std::basic_ostream<_CharT, _Traits>::__ostream_type = std::basic_ostream<char>]
/usr/include/c++/4.6/ostream:215:7: note:   no known conversion for argument 1 from ‘mystruct’ to ‘float’
/usr/include/c++/4.6/ostream:223:7: note: std::basic_ostream<_CharT, _Traits>::__ostream_type& std::basic_ostream<_CharT, _Traits>::operator<<(long double) [with _CharT = char, _Traits = std::char_traits<char>, std::basic_ostream<_CharT, _Traits>::__ostream_type = std::basic_ostream<char>]
/usr/include/c++/4.6/ostream:223:7: note:   no known conversion for argument 1 from ‘mystruct’ to ‘long double’
/usr/include/c++/4.6/ostream:227:7: note: std::basic_ostream<_CharT, _Traits>::__ostream_type& std::basic_ostream<_CharT, _Traits>::operator<<(const void*) [with _CharT = char, _Traits = std::char_traits<char>, std::basic_ostream<_CharT, _Traits>::__ostream_type = std::basic_ostream<char>]
/usr/include/c++/4.6/ostream:227:7: note:   no known conversion for argument 1 from ‘mystruct’ to ‘const void*’
/usr/include/c++/4.6/bits/ostream.tcc:121:5: note: std::basic_ostream<_CharT, _Traits>& std::basic_ostream<_CharT, _Traits>::operator<<(std::basic_ostream<_CharT, _Traits>::__streambuf_type*) [with _CharT = char, _Traits = std::char_traits<char>, std::basic_ostream<_CharT, _Traits>::__streambuf_type = std::basic_streambuf<char>]
/usr/include/c++/4.6/bits/ostream.tcc:121:5: note:   no known conversion for argument 1 from ‘mystruct’ to ‘std::basic_ostream<char>::__streambuf_type* {aka std::basic_streambuf<char>*}’
/usr/include/c++/4.6/bits/basic_string.h:2693:5: note: template<class _CharT, class _Traits, class _Alloc> std::basic_ostream<_CharT, _Traits>& std::operator<<(std::basic_ostream<_CharT, _Traits>&, const std::basic_string<_CharT, _Traits, _Alloc>&)
/usr/include/c++/4.6/ostream:451:5: note: template<class _CharT, class _Traits> std::basic_ostream<_CharT, _Traits>& std::operator<<(std::basic_ostream<_CharT, _Traits>&, _CharT)
/usr/include/c++/4.6/ostream:456:5: note: template<class _CharT, class _Traits> std::basic_ostream<_CharT, _Traits>& std::operator<<(std::basic_ostream<_CharT, _Traits>&, char)
/usr/include/c++/4.6/ostream:462:5: note: template<class _Traits> std::basic_ostream<char, _Traits>& std::operator<<(std::basic_ostream<char, _Traits>&, char)
/usr/include/c++/4.6/ostream:468:5: note: template<class _Traits> std::basic_ostream<char, _Traits>& std::operator<<(std::basic_ostream<char, _Traits>&, signed char)
/usr/include/c++/4.6/ostream:473:5: note: template<class _Traits> std::basic_ostream<char, _Traits>& std::operator<<(std::basic_ostream<char, _Traits>&, unsigned char)
/usr/include/c++/4.6/ostream:493:5: note: template<class _CharT, class _Traits> std::basic_ostream<_CharT, _Traits>& std::operator<<(std::basic_ostream<_CharT, _Traits>&, const _CharT*)
/usr/include/c++/4.6/bits/ostream.tcc:323:5: note: template<class _CharT, class _Traits> std::basic_ostream<_CharT, _Traits>& std::operator<<(std::basic_ostream<_CharT, _Traits>&, const char*)
/usr/include/c++/4.6/ostream:510:5: note: template<class _Traits> std::basic_ostream<char, _Traits>& std::operator<<(std::basic_ostream<char, _Traits>&, const char*)
/usr/include/c++/4.6/ostream:523:5: note: template<class _Traits> std::basic_ostream<char, _Traits>& std::operator<<(std::basic_ostream<char, _Traits>&, const signed char*)
/usr/include/c++/4.6/ostream:528:5: note: template<class _Traits> std::basic_ostream<char, _Traits>& std::operator<<(std::basic_ostream<char, _Traits>&, const unsigned char*)
14
liv2hak

Sie müssen den Operator << für die Klasse mystruct überladen

So etwas wie :-

friend ostream& operator << (ostream& os, const mystruct& m)
{
    os << m.m_a <<" " << m.m_b << endl;
    return os ;
}

Siehe hier

18
P0W

Es gibt nur einen Fehler:

cout.cpp: 26: 29: Fehler: Keine Übereinstimmung für 'operator <<' in 'std :: operator << [with _Traits = std :: char_traits] ((* & std :: cout), ((const char * ) "meine Struktur")) << m '

Dies bedeutet, dass der Compiler für operator<< keine passende Überladung finden konnte. Der Rest der Ausgabe ist der Compiler, der operator<<-Überladungen auflistet, die nicht übereinstimmen. Die dritte Zeile sagt eigentlich Folgendes:

cout.cpp: 26: 29: Anmerkung: Kandidaten sind:

7
Søren Debois

Offensichtlich weiß der von der Standardbibliothek bereitgestellte Operator nicht, was er mit Ihrem benutzerdefinierten Typ mystruct tun soll. Dies funktioniert nur für vordefinierte Datentypen. Um es für Ihren eigenen Datentyp verwenden zu können, müssen Sie operator << überladen, um Ihren benutzerdefinierten Datentyp zu übernehmen.

5
Alok Save

Object ist eine Sammlung von Methoden und Variablen. Sie können die Variablen in object nicht durch die Operation cout drucken. Wenn Sie die Dinge im Objekt anzeigen möchten, müssen Sie entweder eine Getter- oder eine Anzeigetextmethode in der Klasse angeben.

ex

#include <iostream>

using namespace std;

class mystruct

{
private:
    int m_a;
    float m_b;

public:
    mystruct(int x, float y)
    {
            m_a = x;
            m_b = y;
    }
    public:
    void getm_aAndm_b()
    {
        cout<<m_a<<endl;
        cout<<m_b<<endl;
    }



};

int main()
{

    mystruct m = mystruct(5,3.14);

    cout << "my structure " << endl;
    m.getm_aAndm_b();
    return 0;

}

Nicht, dass dies nur eine Möglichkeit ist

0
Nipun Alahakoon