c++ - 运行容器类程序时显示错误

Question

Garden 包含 n 棵苹果树。每棵苹果树都可以表征如下:第一年的收获，过去每年的增加，以及苹果数量每年增加的规律。该定律使用两个系数 coef1 和 coef2。该法则适用于所有苹果树，但系数可能不同。你必须:
a) 找出这几年每棵苹果树结出的苹果数量。年数 从键盘输入或定义为常量值；
b) 找出特定年份每棵苹果树结出的苹果数量；
c) 将在这些年内结出一定数量苹果的苹果树形成新的花园 不小于规定值。苹果数量和年限的值可以是 定义为常量或从键盘输入。
这只是初始部分并给出错误:

Warning 3 warning C4183: 'Print': missing return type; assumed to be a member function returning 'int' c:\users\kumar anubhav\documents\garden\atree.h 11 1 garden

Warning 6 warning C4183: 'Print': missing return type; assumed to be a member function returning 'int' c:\users\kumar anubhav\documents\garden\atree.h 11 1 garden 9 IntelliSense: no operator "<<" matches these operands operand types are: std::ostream << std::string c:\Users\kumar anubhav\Documents\garden\Source.cpp 42 6 garden

Error 2 error C4430: missing type specifier - int assumed. Note: C++ does not support default-int c:\users\kumar anubhav\documents\garden\atree.h 11 1 garden

Error 5 error C4430: missing type specifier - int assumed. Note: C++ does not support default-int c:\users\kumar anubhav\documents\garden\atree.h 11 1 garden

Error 7 error C2556: 'std::string Atree::Print(void)' : overloaded function differs only by return type from 'int Atree::Print(void)' c:\users\kumar anubhav\documents\garden\atree.cpp 9 1 garden

Error 8 error C2371: 'Atree::Print' : redefinition; different basic types c:\users\kumar anubhav\documents\garden\atree.cpp 9 1 garden

Error 1 error C2146: syntax error : missing ';' before identifier 'Print' c:\users\kumar anubhav\documents\garden\atree.h 11 1 garden

Error 4 error C2146: syntax error : missing ';' before identifier 'Print' c:\users\kumar anubhav\documents\garden\atree.h 11 1 garden

class Atree
{
private:
int year, increa;
int coef1, coef2;
 public:
Atree(): year(0), increa(16), coef1(1), coef2(2) { }
Atree(int year, int increa, int coef1, int coef2):
 year(year), increa(increa), coef1(coef1), coef2(coef2) { }
 string Print();
};


#include "Atree.h"
 #include <sstream>
 #include <iomanip>
 using namespace std;
//------------------------------------------------------------
 // Writes data into a line
 string Atree::Print()
 {
stringstream sr;
sr << setw(6) << coef1 << setw(6) << coef2
 << setw(5) << year << setw(7) << increa ;
return sr.str();
 }
#pragma once
//------------------------------------------------------------
#include "Atree.h"
class Garden
{
public:
static const int CMaxi = 100;
 private:
Atree Atrees[CMaxi];
int n;
 public:
Garden():n(0) { }
Atree Get(int i) { return Atrees[i]; }
int Get() { return n; }
void Set(Atree ob) { Atrees[n++] = ob; }
};
//------------------------------------------------------------
#include "Garden.h"
#include <fstream>
#include <iostream>
#include <iomanip>
using namespace std;
//------------------------------------------------------------
const char Cu1[]="U1.txt";
//------------------------------------------------------------
void Read(Garden & Gard, const char fv []);
void Print(Garden & Gard);
//------------------------------------------------------------
int main()
{
 Garden Gard;
 Read(Gard, Cu1);
 Print(Gard);
 return 0;
}
//------------------------------------------------------------
// Reads data from the file fv
void Read(Garden & Gard, const char fv [])
{
    ifstream fd(fv);
 int n;
 fd >> n;
 int coef1, coef2, year, increa;
 for (int i = 0; i < n; i++) {
 fd >> coef1 >> coef2 >> year >> increa;
 Gard.Set(Atree(year, increa, coef1, coef2));
 }
 fd.close();
 }
//------------------------------------------------------------
// Prints the data of object Gard
 void Print(Garden & Gard)
 {
 cout << " Information on apple trees\n";
 cout << " Coef1 coef2 year increa\n";
 for (int i = 0; i < Gard.Get(); i++)
cout << Gard.Get(i).Print() << endl;
}
//------------------------------------------------------------

Answer 1

在Atree的声明中，您已经声明了一个名为 Print 的方法返回 string .编译器不知道什么是 string是的，并且与 C 语言不同，它不能将返回类型默认为 int .您可能打算使用 std::string并因此写:

class Atree
{
std::string Print();
};

您可能需要 #include <string>事先。

编译器也在提示，因为你对 Atree::Print 的定义的返回类型不同。在这里它知道您正在尝试使用 std::string因为你带来了std命名空间与 using 的上下文关键词:

using namespace std;
string Atree::Print()
{
}

编译器知道你希望返回一个 std::string , 但这不同于 Atree::Print声明，其中编译器假定您正在尝试返回 int .

你应该避免 using namespace std .这样做只会给你关于编译器不知道什么是 string 的错误。这会(希望)让它更容易解决。