在类中设置和获取对象的方法

Question

我有一个 Result 类，它将另外两个类 UNIT 和 Date 作为对象参数，以便我可以将值存储在其中以用于这些类。我会记下我到目前为止所得到的，我得到的一些错误如下。

error: prototype for 'int Result::GetUnit() const' does not match any in class 'Result'|
lab2\Result.h|17|error: candidate is: Result Result::GetUnit() const|
lab2\Result.cpp|66|error: prototype for 'int Result::GetDate()' does not match any in class 'Result'|
lab2\Result.h|18|error: candidate is: Result Result::GetDate() const|
lab2\Result.cpp|73|error: 'SetResult' was not declared in this scope|
error: 'SetResult' was not declared in this scope|

对于错误not declared in this scope，经过研究我了解到我需要在第一次调用之前定义函数。我已经在 .cpp 文件中完成了该操作，但仍然出现错误。我做错了什么？

结果.h：

#ifndef RESULT_H
#define RESULT_H

#include <iostream>
#include <string>
#include "UNIT.h"
#include "Date.h"


//const unsigned ResultSize = 10;
using namespace std;
class Result
{
    public:
        Result(){};
        Result(UNIT unitobj1, unsigned marks1, Date dateobj1);
        Result GetUnit() const;
        Result GetDate() const;
        void SetDate(Date dateobj1);
        void SetUnit(UNIT unitonj1);
        void SetMarks( unsigned marks1 );
        unsigned GetMarks() const;

        void SetCredits( unsigned cred );
        unsigned GetCredits() const;

        string GetID() const;
        void SetID(string idd);


        void SetResult(istream & input);
        void GetResult(ostream & os);//unsigned GetUnit() const;


    private:

        UNIT unitobj;
        Date dateobj;
        string id;
        int credits;
        unsigned marks;

};
inline unsigned Result::GetCredits() const
{
  return credits;
}

ostream & operator <<( ostream & os, const Result & S);
istream & operator >>( istream & input, Result & S);

#endif // RESULT_H

结果.cpp：

#include "Result.h"
#include "UNIT.h"
#include "Date.h"

Result::Result(UNIT unitobj1, unsigned marks1, Date dateobj1)
{

    unitobj = unitobj1;
    marks = marks1;
    dateobj = dateobj1;

}

void Result::SetResult(istream &input){

    UNIT unitobj1;
    unsigned marks1;
    Date date1;

    input >> unitobj1 >> marks1 >> date1;

    SetUnit(unitobj1);
    SetMarks(marks1);
    SetDate(date1);

}



void Result::GetResult(ostream &os){

    os << GetUnit() < "  Marks: " << GetMarks() << '\n' << GetDate() << '\n';

}

void Result::SetUnit(UNIT unitobj1){

    unitobj = unitobj1;

}

void Result::SetMarks(unsigned marks1){

    marks = marks1;

}

void Result::SetDate(Date dateobj1){

    dateobj = dateobj1;

}

Result::GetUnit() const{

    return unitobj;

}

inline unsigned Result::GetMarks() const{

    return marks;

}

Result::GetDate(){

    return dateobj;

}
istream & operator >>( istream & input, Result & S)
{
      SetResult(input);
      return input;

}

ostream & operator <<( ostream & os, const Result & S)
{
      GetResult(os);
      return os;
}

日期.h：

#if !defined(_DATE_H)
#define _DATE_H

#include <iostream>
#include <string>

using namespace std;

class Date {
public:
    Date();
    Date(unsigned day1, string month1, unsigned year1);

    void SetDay(unsigned day1);
    void SetMonth(string month1);
    void SetYear(unsigned year1);
    unsigned GetDay() const;
    string GetMonth() const;
    unsigned GetYear() const;

    void SetDate(istream &input);
    void GetDate(ostream & os);


private:

    unsigned day;
    string month;
    unsigned year;

};

 ostream & operator <<(ostream & os, const Date & D);
 istream & operator >>(istream & input, Date & D);
#endif  //_DATE_H

日期.cpp：

//
//
//  Generated by StarUML(tm) C++ Add-In
#include "Date.h"

Date::Date(unsigned day1, string month1, unsigned year1) {

    day = day1;
    month = month1;
    year = year1;

}


void Date::SetDay(unsigned day1) {

    day = day1;

}

void Date::SetMonth(string month1) {

    month = month1;

}

void Date::SetYear(unsigned year1) {

    year = year1;

}

inline unsigned Date::GetDay() const {

    return day;

}

string Date::GetMonth() const {

    return month;

}

inline unsigned Date::GetYear() const {

    return year;

}
void Date::SetDate(istream &input){

    unsigned day1;
    string month1;
    unsigned year1;


    input >> day1 >> month1 >> year1;
    SetDay(day1);
    SetMonth(month1);
    SetYear(year1);

}

void Date::GetDate(ostream &os){

    os << "  Date: " << GetDay() << " " << GetMonth() << " " << GetYear();

}


istream & operator >>( istream & input, Date & D) {

    SetDate(input);
    return input;

}

ostream & operator <<( ostream & os, const Date & D) {

    GetDate(os);

    return os;

}

UNIT.h：

        #ifndef UNIT_H
        #define UNIT_H

        #include <iostream>
        #include <string>  // C string library

        using namespace std;



        const unsigned UnitNameSize = 10;

        class UNIT
        {
        public:
          UNIT();
          UNIT( string nam, string idd, unsigned cred);

          void SetName(string nam);
          string GetName() const;

          void SetMarks(unsigned marks1);
          unsigned GetMarks();

          void SetCredits(unsigned cred);
          unsigned GetCredits() const;

          string GetID() const;
          void SetID(string idd);

          void SetUnit(istream & input);
          void GetUnit(ostream & os);

        private:


          string name;  
          string id;   
          unsigned marks;
          int credits;
        };

        ostream & operator <<( ostream & os, const UNIT & U);
        istream & operator >>( istream & input, UNIT & U);



        #endif // UNIT_H

UNIT.cpp：

#include "UNIT.h"
#include <string>

UNIT::UNIT()
{
  name[0] = '\0';
}

void UNIT::SetName(string nam)
{
  name = nam;
}


string UNIT::GetName() const
{
  return name;
}

void UNIT::SetID(string idd)
{
  id = idd;
}


string UNIT::GetID() const
{
  return id;
}

void UNIT::SetCredits(unsigned cred){

    credits = cred;

}

inline unsigned UNIT::GetCredits() const{

    return credits;

}
UNIT::UNIT( string nam, string idd,
                unsigned cred)
{
  name.replace(0, 10, nam );
  id = idd;
  credits = cred;
}

void UNIT::SetUnit(istream &input){

  string nam;
  string idd;
  unsigned cred;

  getline(input,nam, '\n');
  getline(input,idd,'\n');
  input >> cred;

  SetName(nam);
  SetID(idd);
  SetCredits(cred);

}

void UNIT::GetUnit(ostream & os){

  os << "  Unit ID:  " << GetID() << '\n'
     << "  Unit Name: " << GetName() << '\n'
     << "  Credits: " << GetCredits() << '\n';

}


istream & operator >>( istream & input, UNIT & U)
{
  SetUnit(input);

  return input;
}

ostream & operator <<( ostream & os, const UNIT & U)
{
  GetUnit(os);
  return os;
}

注意：我知道我可以只创建类的重载运算符方法并将它们声明为朋友，但我试图通过使用 set 和 get 方法来实现这一点。任何帮助将不胜感激！

Answer 1

所以，这很简单，看看Result::GetUnit

Result::GetUnit() const {
    return unitobj;
}

此方法缺少返回类型。现在看unitobj

UNIT unitobj;

所以很明显返回类型应该是UNIT，所以上面的方法应该定义为

UINT Result::GetUnit() const {
    return unitobj;
}

现在看看你是如何在你的类中声明这个方法的

class Result
{
    ...
    Result GetUnit() const;

这里你给它一个返回类型Result，我们已经看到返回类型应该是UINT，所以把上面的改成

class Result
{
    ...
    UNIT GetUnit() const;

Result::GetDate 也有类似的问题，这里的返回类型应该是Date，但你再次指定它为Result。

对于SetResult 错误，您只需指定您正在对Result 对象调用SetResult 方法。编译器认为您正在调用全局 SetResult 函数（不存在）

这样

istream & operator >>( istream & input, Result & S)
{
      S.SetResult(input);
      return input;
}

S.SetResult(input); 告诉编译器您要使用S 引用的Result 对象调用SetResult 方法。

您可以通过仔细阅读错误消息来判断这一点，它说的是'SetResult' was not declared in this scope，而不是'Result::SetResult' was not declared in this scope。正如你所说，你已经声明了Result::SetResult，但你的代码没有调用它，它试图调用另一个名为SetResult 的函数，编译器正确报告没有声明这样的函数。