动态数组，动态构造函数

Question

I would like to get some good information about the themes mentioned in the title.

So, I would like to get some good notes/tutorials about how to create a dynamic class constructor and save the class instances in a dynamic array which will be defined by the user. I'd like to achive the fallowing problem:

"A family wants to manage its monthly expenses. In order to complete this task, the family needs an application to store, for a certain month, all the family's expenses. Each expense will be stored in the application through the following elements: day (of the month in which it was made), amount of money and the type of the expense (the family wants to group its expenses in the following categories: house keeping, food, transport, clothing, telephone&internet, others – books, films, sports, etc). The family needs an application in order to repeatedly execute the following functionalities (each functionality is exemplified):"

Thank you. PS: I'd like to mention i`m new to c++, but having knowledge about OOP from python.

EDIT: i got this far by now.

 class ExpC
  {
private:
int *days;
int *houseK;
int *food;
int *transp;
int *cloth;
int *telNet;
int *others;

public:
/* constructor */

ExpC()                 //Constructor
{
int *days,* houseK,*food,*transp,*cloth,*telNet,*others;
}

~ExpC()                //Deconstructor
{

}

void add(){

}

 };

Answer 1

It seems to me like you need:

1) A base class - Expense . You can extend this if needed, or use it as-is.

2) A container of pointers or, better yet, smart pointers to Expense objects. Look up std::vector or std::map if you need fast lookup by some argument.

3) Create new expenses dynamically with new : new Expense() .

4) Add to the container:

std::vector<Expense*> expenses;
expenses.push_back(new Expense());

and free the memory when you are done.

EDIT:

Since your code is completely wrong, I suggest reading a good C++ book or tutorial, and then take the approach I suggested.

Answer 2

It sounds to me like you need to look into creating a structure that holds the budget information (month, food, transportation, etc). Then, if you can use the STL, look into creating a vector of your structure which would easily allow you to create expense data for as many months as the user requires. And then wrap that all up in a class to create methods for the functionality.

Research the STL vector class. A vector is a dynamic array that can be of any type from a basic data type such as an integer to something more complex like a user-defined data type (in your case, an expense structure). Research vectors. They are fairly easy to implement and use if you are already familiar with arrays.

But please provide a little more information as to what you can and can't do.

Answer 3

My DB coding experience says me to put each of expences in separate record (object)

So better would be like that

class Expence {
public:
  enum Type {k_food, k_house, k_transport /*, etc*/};

  Expence (int date, Type type, float amount) :
  date_(date),
  type_(type),
  amount_(amount)
  {}

private:
  int date_; 
  Type type_; 
  float amount_;
};

Add to it all methods you need.

The rest of the program will be look like Luchian Grigore says.

Hope it helps.