Using Variables for Intelligent Accessor Functions?

[phummon]

Hello everyone,

I’m an intermediate-level C++ programmer grappling with a fairly rudimentary problem. I’m creating a C++ object called FruitCart; FruitCart contains a number of integers categorizing the numbers of individual fruit in the cart. I also need FruitCart to contain accessor functions so other functions can set, retrieve, and print the fruit values. Here’s what I have so far:

--------------------------------------------------------------------------------------
class FruitCart {
  public:
    // Constructors
    FruitCart();
    ~FruitCart();

    // Accessors
    void SetApples(int a)  {Apples=a;}
    int GetApples()        {return Apples;}
    void PrintApples()     {cout<<Apples;}

    // Need accessor functions like the above for all kinds of fruit

  protected:
    int Apples;   // Number of Apples in the cart
    int Oranges;  // Number of Oranges in the cart
    int Bananas;  // Number of Bananas in the cart
    int Plums;    // Number of Plums in the cart

    // May have nearly 50 kinds of fruit!

};
--------------------------------------------------------------------------------------

The problem I have is that I may have over fifty kinds of fruit in the cart! It would be a big pain to manually write out accessor functions for each kind of fruit.

I’m searching for a more intelligent solution. What I’d like to have is a general accessor function where I pass in the name of the fruit as a string (specifically, as a char * pointer) and leave everything else the same. Put in quasi-psuedocode:

--------------------------------------------------------------------------------------
class FruitCart {
  public:
    // Constructors
    FruitCart();
    ~FruitCart();

    // Accessors
    void SetFruit(int a, char * FruitType)
    int GetFruit(char * FruitType)
    void PrintFruit(char * FruitType)

  protected:
    int Apples;   // Number of Apples in the cart
    int Oranges;  // Number of Oranges in the cart
    int Bananas;  // Number of Bananas in the cart
    int Plums;    // Number of Plums in the cart

};

void FruitCart::SetFruit(int a, char * FruitType)
  {  ${FruitType} = a;  }
int FruitCart::GetFruit(char * FruitType)
  {  return ${FruitType};  }
void FruitCart::PrintFruit(char * FruitType)
  {  cout << ${FruitType};  }
--------------------------------------------------------------------------------------

Hopefully this makes sense. I know this would be simple to do in UNIX, so I’m hoping there’s a (relatively) simple way to do this in C++.

Many thanks!
-Pete

[mbulow]

Hi phummon

You should consider using the std::map to map from a string to an int.

A quick rewrite of your class using map:

#include <iostream>
#include <map>
#include <string>

class FruitCart {
  public:
    // Constructors
    FruitCart();
    ~FruitCart();

    // Accessors
	void SetFruit(int a, std::string FruitType);
	int GetFruit(std::string FruitType);
	void PrintFruit(std::string FruitType);

  protected:
	  std::map<std::string, int> FruitCount;
};

void FruitCart::SetFruit(int a, std::string FruitType)
{
	FruitCount[FruitType] = a;
}
int FruitCart::GetFruit(std::string FruitType)
{
	return FruitCount[FruitType];
}
void FruitCart::PrintFruit(std::string FruitType)
{
	std::cout << GetFruit(FruitType);
}

[chiwawa10]

Yes, I agree with mbulow that you can use a std::map. You may also want to consider the option of 2D array since the number of fruits supported in a cart is known at compile time.

[phummon]

Nice! This is great advice, I really appreciate your help. This solves a lot of problems for me! :)

Many thanks!
-Pete