C++如何在头文件中声明一个向量，在构造函数中设置大小，然后访问

Question

I am having issues declaring a vector in the header, setting the default size in the constructor, then making it a function to do stuff in aDie.cpp. My known error is under the aDie.cpp declaration is incompatible for void aDie::Frequency(std::vector<int> Vector()); . Any help would be appreciated to get me going in the right direction so that I have a vector that I can add values into. My code is below.

header aDie.h

#define aDie_H   
#include <vector>
class aDie {
public: 
    int i = 0; 
    aDie();
    void numRolls();
    void getSeed();
    void roll(); 
    void Frequency(std::vector<int> Vector());


private:
    int Rolls;
    int dSeed;
    int die1;
    int die2;
    int sum;

}; 

cpp aDie.cpp

#include "aDie.h"  
#include <iostream>  
#include <ctime>  
#include <vector>
using namespace std;

aDie::aDie() { //constructor sets values to default 0
    die1 = 0;
    die2 = 0;
    dSeed = 0;
    vector<int> Vector(6); //defaults to size six 
}
void aDie::numRolls() {
    cout << "Enter number of times for die to be rolled: ";
    cin >> Rolls;
    return;
}
void aDie::getSeed() {  //gets seed 
    cout << "Enter desired seed number: ";
    cin >> dSeed;
    srand(dSeed);
    return;
}
void aDie::roll() { //rng for one die
    die1 = 1 + rand() % 6;
}
void aDie::Frequency(std::vector<int> Vector()); //store the rolls output by aDie::roll


}

.cpp Main.cpp

#include <iostream>
using namespace std;

#include "aDie.h"   
#include "aHistogram.h"
#include <iostream> 
#include <vector>
using namespace std;

void game1();

int main() {
    game1();

    system("Pause");
}

void game1() {
    int i = 0;
    int Rolls = 0;

    cout << "Enter number of times for die to be rolled: ";
    cin >> Rolls;

    aDie Roll1; //calls default constructor
    Roll1.getSeed(); //calls seed  

    for (i = 0; i < Rolls; i++) {
        Roll1.roll(); //rolls die
        Roll1.//whatever my vector will be called

    }
}

Answer 1

The code

void Frequency(std::vector<int> Vector());

is indeed invalid syntax, what you probably want to do is

void Frequency(std::vector<int> &v);

or

void Frequency(const std::vector<int> &v);

If you want to store the vector, then it should be member of the class:

class aDie {
//...

private:
    int Rolls;
    int dSeed;
    int die1;
    int die2;
    int sum;
    std::vector<int> vect;

};

and then the constructor could look like:

aDie::aDie()
    //constructor sets values to default 0
    : die1(0)
    , die2(0)
    , dSeed(0)
    , vect(6) //defaults to size six 
{}

Answer 2

I'm not sure if this is your other doubt.

In header:

class aDie {
public: 
    int i = 0; 
    vector<int> Vector;
    aDie();
    void numRolls();
    void getSeed();
    void roll(); 
    void Frequency(const vector<int>& Vector);

private:
    int Rolls;
    int dSeed;
    int die1;
    int die2;
    int sum;

};

In .cpp:

aDie::aDie() { //constructor sets values to default 0
    die1 = 0;
    die2 = 0;
    dSeed = 0;
    Vector = vector<int>(6); //defaults to size six 
}

Answer 3

I recommend you start reading up on the basics eg here (especially chapter 8).

But to answer your question, I try to give you a short walkthrough in the comments of the code.

// Header file A.h
#include <vector>
class A {
public:
    A();   
    void addNumbers();
    void addNumberIntoAnyVector(std::vector<int>& vec);

private:
    std::vector<int> myVector;
};

// A.cpp
#include "A.h"

// First option, initialize the member before the body executes.
// See e.g. http://www.cprogramming.com/tutorial/initialization-lists-c++.html
A::A() : myVector(6) {
}

// Second option, resize it inside the body of you contructor
// Use only one of them, not both!
A::A() {
    myVector.resize(6);
}

// You have access to your member variables from within any member function
// So simply numbers to your myVector here.
void A::addNumbers() {
    for(int i=0; i<myVector.size(); ++i)
        myVector[i] += i;
}

// In this version you can pass any vector<int> instance as an argument
// and fill it with numbers.
void addNumberIntoAnyVector(std::vector<int>& vec) {
    for(int i=0; i < vec.size(); ++i)
        vec[i] += i;
}

If that doesn't make sense to you, you should go back even further in the tutorials. I would really suggest to get some foundational knowledge first.

Answer 4

If I understand correctly, you want to store the results of die rolls and their associated frequencies of occurrence in a container? If so, then this should achieve what you want (ignoring irrelevant methods):

#define A_DIE_H
#ifndef A_DIE_H

#include <map>  // for std::map
#include <utility> // for std::pair / std::make_pair

class aDie {
public: 
    aDie();
    void roll(); 
    int getFrequency(int _res) const;

private:
    // stores die roll results as Keys and frequency
    // of occurrence as Values
    std::map<int, int> result_freq_map;
};

#endif /* A_DIE_H */

and in the implementation file:

#include "aDie.h"   

aDie::aDie() { 

}

void aDie::roll() { //rng for one die
    int die1 = 1 + rand() % 6;  // roll the dice

    // try inserting result into map with occurrence of 1
    if (result_freq_map.insert(std::make_pair(die1,1)).second) {
        return;
    }
    // if result already contained in map, increment its associated value
    result_freq_map[die1]++;
}

// gets the frequency of occurrence of a given result _res
int aDie::getFrequency(int _res) const { 
    return result_freq_map[_res];
}

This is untested but it should work. I can address the rest of your code and how it could be structured better if you like as well.