Error In classes C++ - c++

Question

I have to make a program to display the weather in Sheffield since 1930.
I have to use sheffield.data for the record.
I have 3 files. Data.cpp, Data.hpp and analyze.cpp
analyze.cpp:
#include <istream>
#include <fstream>
#include <vector>
#include "data.hpp"
using namespace std;
int main()
{
MonthData data();
vector<MonthData> vectorData;
ifstream file ("sheffield.data");
string line;
int l_num = 0;
if (file.is_open()) {
while (getline(file, line))
if (l_num < 4) {
l_num += 1;
}
else {
file >> data;
vectorData.push_back(data);
}
float MinimumDeg = vectorData[0].getMinimum();
int year = vectorData[0].getYear();
for ( size_t a = 0; a < vectorData.size(); a++)
{
MinimumDeg = vectorData[a].getMinimum();
year = vectorData[a].getYear();
}
cout << "Lowest year and month lowest rainfall: '\n'" << "Min Temp;" << MinimumDeg << "C '\n'" << "Year" << year << endl;
return 0;
}
}
:
data.cpp
#include "data.hpp"
#include <iostream>
using namespace std;
istream& operator >> (istream& in, MonthData& data)
{
in >> data.year >> data.year >> data.temp_maximum >> data.temp_minimum >> data.air_frost >> data.rain >> data.sun;
return in;
}
data.hpp:
#ifndef DATA_HPP
#define DATA_HPP
#include <iostream>
#include <string>
#include <cmath>
using namespace std;
class MonthData
{
friend istream& operator >> (istream&, MonthData&);
public:
//overload constructor
MonthData(double, int, double, double, int, double, double);
//Accessor functions
double getYear() const { return year; } //returns the year
int getMonth() const { return month; } //returns the month
double getMaximum() const { return temp_maximum; } //returns maximum temperature
double getMinimum() const { return temp_minimum; } //returns minimum temperature
int getFrost() const { return air_frost; } //returns air frost
double getRain() const { return rain; } //returns rainfall
double getSun() const { return sun; } //returns no of hours of sunshine
private:
double year;
double month;
double temp_maximum;
double temp_minimum;
int air_frost;
double rain;
double sun;
};
#endif
Why am I getting this error?
[sc14da#cslin035 cw]$ g++ data.cpp data.hpp analyze.cpp -o analyze
analyze.cpp: In function ‘int main()’:
analyze.cpp:11: error: no matching function for call to ‘MonthData::MonthData()’
data.hpp:17: note: candidates are: MonthData::MonthData(double, int, double, double, int, double, double)
data.hpp:12: note: MonthData::MonthData(const MonthData&)

Answer 1

If you do not provide any constructor in your class, the compiler will automatically create one for you.
In your class, you have specified a particular constructor:
MonthData(double, int, double, double, int, double, double);
As soon as you provide any constructor, the compiler will not create a default constructor (i.e. one that takes no parameters).
You are calling
MonthData data();
You are passing no parameters here but you have no constructor that takes no parameters.
You probably meant to call
MonthData data(with 7 parameters);
Alternatively, add the following to your MonthData class body:
MonthData();
Then in your data.cpp, need to provide the code for what this constructor should do, i.e.
MonthData::MonthData()
{
//Initialise as required - but better to use a member initialization list
}
It would be better to use a member initialization list for your 7 member variables.
For example:
MonthData::MonthData()
: year(2014), month(2), temp_maximum(15.4), temp_minimum(2.1), air_frost(5), rain(5.6), sun(7.6) //Use desired default values
{}
This simple constructor code could instead be put directly in the class body in the header file:
class MonthData
{
public:
//overload constructor
MonthData(double y, int m, double max, double min, int fr, double r, double s)
: year(y), month(m), temp_maximum(max), temp_minimum(min), air_frost(fr), rain(r), sun(s) {};
//default constructor
MonthData()
: year(2014), month(2), temp_maximum(15.4), temp_minimum(2.1), air_frost(5), rain(5.6), sun(7.6) {};
etc
};
In addition - review your variable types. Should year really be a double? Also you have month declared as a double but your accessor returns an int.

Answer 2

That's not surprising as you haven't included a default constructor. Or, more specifically, a constructor that matches this line:
MonthData data();
Solution: add a default constructor in your base MonthData class (data.hpp).