Question

我对超视镜+有问题。

这是我的代码：

class Odcinek : public Figura
{
public:
    Odcinek(int ile,string imie,char znak): Figura(ile,imie,znak){}
    friend Odcinek& operator+(int liczba);
    virtual void wypisz() const;
};

Odcinek& operator+(int liczba);
{
    Odcinek Od;
    Od.ile = Od.ile+liczba;
    Od.imie = imie;
    Od.znak = znak;
    return Od;
}

我希望它能工作：

Odcinek F3(5,"Odcinek drugi",'*');

F3+3;

||=== Build: Debug in Figura (compiler: GNU GCC Compiler) ===|
include\Figura.h|29|error: 'Odcinek& operator+(int)' must have an argument of class or enumerated type|
C:\Users\mkkar\Desktop\Programowanie obiektowe ~kolokwium\Figura\main.cpp||In function 'int main()':|
C:\Users\mkkar\Desktop\Programowanie obiektowe ~kolokwium\Figura\main.cpp|15|error: no match for 'operator+' (operand types are 'Odcinek' and 'int')|
c:\mingw\lib\gcc\mingw32\6.3.0\include\c++\bits\stl_iterator.h|341|note: candidate: template std::reverse_iterator std::operator+(typename std::reverse_iterator::difference_type, const std::reverse_iterator&)|
c:\mingw\lib\gcc\mingw32\6.3.0\include\c++\bits\stl_iterator.h|341|note:   template argument deduction/substitution failed:|
include\Figura.h|29|error: 'Odcinek& operator+(int)' must have an argument of class or enumerated type|
C:\Users\mkkar\Desktop\Programowanie obiektowe ~kolokwium\Figura\src\Figura.cpp|67|error: 'Odcinek& operator+(int)' must have an argument of class or enumerated type|
C:\Users\mkkar\Desktop\Programowanie obiektowe ~kolokwium\Figura\src\Figura.cpp|68|error: expected unqualified-id before '{' token|
C:\Users\mkkar\Desktop\Programowanie obiektowe ~kolokwium\Figura\main.cpp|15|note:   mismatched types 'const std::reverse_iterator' and 'int'|
c:\mingw\lib\gcc\mingw32\6.3.0\include\c++\bits\stl_iterator.h|1200|note: candidate: template std::move_iterator std::operator+(typename std::move_iterator::difference_type, const std::move_iterator&)|
c:\mingw\lib\gcc\mingw32\6.3.0\include\c++\bits\stl_iterator.h|1200|note:   template argument deduction/substitution failed:|
C:\Users\mkkar\Desktop\Programowanie obiektowe ~kolokwium\Figura\main.cpp|15|note:   mismatched types 'const std::move_iterator' and 'int'|
c:\mingw\lib\gcc\mingw32\6.3.0\include\c++\bits\basic_string.h|4929|note: candidate: template std::__cxx11::basic_string std::operator+(const std::__cxx11::basic_string&, const std::__cxx11::basic_string&)|
c:\mingw\lib\gcc\mingw32\6.3.0\include\c++\bits\basic_string.h|4929|note:   template argument deduction/substitution failed:|
C:\Users\mkkar\Desktop\Programowanie obiektowe ~kolokwium\Figura\main.cpp|15|note:   'Odcinek' is not derived from 'const std::__cxx11::basic_string'|
c:\mingw\lib\gcc\mingw32\6.3.0\include\c++\bits\basic_string.tcc|1147|note: candidate: template std::__cxx11::basic_string std::operator+(const _CharT*, const std::__cxx11::basic_string&)|
c:\mingw\lib\gcc\mingw32\6.3.0\include\c++\bits\basic_string.tcc|1147|note:   template argument deduction/substitution failed:|
C:\Users\mkkar\Desktop\Programowanie obiektowe ~kolokwium\Figura\main.cpp|15|note:   mismatched types 'const _CharT*' and 'Odcinek'|
c:\mingw\lib\gcc\mingw32\6.3.0\include\c++\bits\basic_string.tcc|1163|note: candidate: template std::__cxx11::basic_string std::operator+(_CharT, const std::__cxx11::basic_string&)|
c:\mingw\lib\gcc\mingw32\6.3.0\include\c++\bits\basic_string.tcc|1163|note:   template argument deduction/substitution failed:|
C:\Users\mkkar\Desktop\Programowanie obiektowe ~kolokwium\Figura\main.cpp|15|note:   mismatched types 'const std::__cxx11::basic_string' and 'int'|
c:\mingw\lib\gcc\mingw32\6.3.0\include\c++\bits\basic_string.h|4966|note: candidate: template std::__cxx11::basic_string std::operator+(const std::__cxx11::basic_string&, const _CharT*)|
c:\mingw\lib\gcc\mingw32\6.3.0\include\c++\bits\basic_string.h|4966|note:   template argument deduction/substitution failed:|
C:\Users\mkkar\Desktop\Programowanie obiektowe ~kolokwium\Figura\main.cpp|15|note:   'Odcinek' is not derived from 'const std::__cxx11::basic_string'|
c:\mingw\lib\gcc\mingw32\6.3.0\include\c++\bits\basic_string.h|4982|note: candidate: template std::__cxx11::basic_string std::operator+(const std::__cxx11::basic_string&, _CharT)|
c:\mingw\lib\gcc\mingw32\6.3.0\include\c++\bits\basic_string.h|4982|note:   template argument deduction/substitution failed:|
C:\Users\mkkar\Desktop\Programowanie obiektowe ~kolokwium\Figura\main.cpp|15|note:   'Odcinek' is not derived from 'const std::__cxx11::basic_string'|
c:\mingw\lib\gcc\mingw32\6.3.0\include\c++\bits\basic_string.h|4994|note: candidate: template std::__cxx11::basic_string std::operator+(std::__cxx11::basic_string&&, const std::__cxx11::basic_string&)|
c:\mingw\lib\gcc\mingw32\6.3.0\include\c++\bits\basic_string.h|4994|note:   template argument deduction/substitution failed:|
C:\Users\mkkar\Desktop\Programowanie obiektowe ~kolokwium\Figura\main.cpp|15|note:   'Odcinek' is not derived from 'std::__cxx11::basic_string'|
c:\mingw\lib\gcc\mingw32\6.3.0\include\c++\bits\basic_string.h|5000|note: candidate: template std::__cxx11::basic_string std::operator+(const std::__cxx11::basic_string&, std::__cxx11::basic_string&&)|
c:\mingw\lib\gcc\mingw32\6.3.0\include\c++\bits\basic_string.h|5000|note:   template argument deduction/substitution failed:|
C:\Users\mkkar\Desktop\Programowanie obiektowe ~kolokwium\Figura\main.cpp|15|note:   'Odcinek' is not derived from 'const std::__cxx11::basic_string'|
c:\mingw\lib\gcc\mingw32\6.3.0\include\c++\bits\basic_string.h|5006|note: candidate: template std::__cxx11::basic_string std::operator+(std::__cxx11::basic_string&&, std::__cxx11::basic_string&&)|
c:\mingw\lib\gcc\mingw32\6.3.0\include\c++\bits\basic_string.h|5006|note:   template argument deduction/substitution failed:|
C:\Users\mkkar\Desktop\Programowanie obiektowe ~kolokwium\Figura\main.cpp|15|note:   'Odcinek' is not derived from 'std::__cxx11::basic_string'|
c:\mingw\lib\gcc\mingw32\6.3.0\include\c++\bits\basic_string.h|5018|note: candidate: template std::__cxx11::basic_string std::operator+(const _CharT*, std::__cxx11::basic_string&&)|
c:\mingw\lib\gcc\mingw32\6.3.0\include\c++\bits\basic_string.h|5018|note:   template argument deduction/substitution failed:|
C:\Users\mkkar\Desktop\Programowanie obiektowe ~kolokwium\Figura\main.cpp|15|note:   mismatched types 'const _CharT*' and 'Odcinek'|
c:\mingw\lib\gcc\mingw32\6.3.0\include\c++\bits\basic_string.h|5024|note: candidate: template std::__cxx11::basic_string std::operator+(_CharT, std::__cxx11::basic_string&&)|
c:\mingw\lib\gcc\mingw32\6.3.0\include\c++\bits\basic_string.h|5024|note:   template argument deduction/substitution failed:|
C:\Users\mkkar\Desktop\Programowanie obiektowe ~kolokwium\Figura\main.cpp|15|note:   mismatched types 'std::__cxx11::basic_string' and 'int'|
c:\mingw\lib\gcc\mingw32\6.3.0\include\c++\bits\basic_string.h|5030|note: candidate: template std::__cxx11::basic_string std::operator+(std::__cxx11::basic_string&&, const _CharT*)|
c:\mingw\lib\gcc\mingw32\6.3.0\include\c++\bits\basic_string.h|5030|note:   template argument deduction/substitution failed:|
C:\Users\mkkar\Desktop\Programowanie obiektowe ~kolokwium\Figura\main.cpp|15|note:   'Odcinek' is not derived from 'std::__cxx11::basic_string'|
c:\mingw\lib\gcc\mingw32\6.3.0\include\c++\bits\basic_string.h|5036|note: candidate: template std::__cxx11::basic_string std::operator+(std::__cxx11::basic_string&&, _CharT)|
c:\mingw\lib\gcc\mingw32\6.3.0\include\c++\bits\basic_string.h|5036|note:   template argument deduction/substitution failed:|
C:\Users\mkkar\Desktop\Programowanie obiektowe ~kolokwium\Figura\main.cpp|15|note:   'Odcinek' is not derived from 'std::__cxx11::basic_string'|
||=== Build failed: 5 error(s), 0 warning(s) (0 minute(s), 1 second(s)) ===|

Answer 1

您的代码中有很多问题

1）您的运算符定义中还有一个分号

Odcinek& operator+(int liczba);
                              ^

2）您的operator+仅具有一个参数，但是您的代码使用了两个参数。我认为解决方案是不要使其成为朋友函数。或者，您可以将其保留为好友，但添加第二个参数。但是，这将需要对已编写的代码进行更多更改。

3）您对operator+的实现似乎使用了未初始化的值

    Odcinek Od;
    Od.ile = Od.ile+liczba;

我猜应该是

    Odcinek Od;
    Od.ile = ile+liczba;

4）最后，最重要的是，您的operator+返回对不再存在的对象的引用

Odcinek& operator+(int liczba)
{
    Odcinek Od; // Od created here
    Od.ile = ile+liczba;
    Od.imie = imie;
    Od.znak = znak;
    return Od;
} // Od destroyed here

但是您返回对已经销毁的Od对象的引用。答案是返回一个值，而不是引用。当您按值返回Od对象的副本并返回该副本时，Od被销毁并不重要。

这是一个更好的版本，它是否有效取决于您尚未向我们展示的代码，但请尝试一下。

class Odcinek : public Figura
{
public:
    Odcinek(int ile,string imie,char znak): Figura(ile,imie,znak){}
    Odcinek operator+(int liczba) const;
    virtual void wypisz() const;
};

Odcinek Odcinek::operator+(int liczba) const
{
    Odcinek Od;
    Od.ile = ile+liczba;
    Od.imie = imie;
    Od.znak = znak;
    return Od;
}

如何修复重载操作数+？

1 个答案: