Solved

constructor and destructor

Posted on 2004-04-20
3
514 Views
Last Modified: 2010-04-01
I am told to write a constructor which accepts data from a file and writes it to a node and a destructor which reads data from the node to a file. I am not knowing what to pass as parameter for the destructors. Could you please give me a sample code. For example reading dates from file to date objects and a destructor reading the date objects and writing them to files.
0
Comment
Question by:rmvprasad
3 Comments
 
LVL 9

Expert Comment

by:Cayce
ID: 10870972
Something like this:

class MyClass {
private:
  Node MyNode;
  string FileName;
public:
  MyClass(string FileName) {
    this->FileName = FileName;
    // open file (filename) and write info to node
  }
  void ~MyClass() {
    // write node info to file (filename)
  }
};

Destructors never accept parameters, however all the object data is still valid at the time the destructor is called (unless it;s dynamically allocated and previously released).

This looks like homework, remember EE policies.
0
 
LVL 2

Expert Comment

by:guntherothk
ID: 10871203
The purpose of a destructor is to clean up the resources allocated to a class instance before the instance is destroyed. The destructor doesn't need parameters because everything it needs to know is in the class instance. The most usual thing that happens in a destructor is to free memory or file handles owned by the instance.
0
 
LVL 5

Accepted Solution

by:
allmer earned 40 total points
ID: 10871845
I assume that 'node' would be a node in, say a linked list.
#include <list>
using namespace std;
class MyClass {
typedef list<int> nodeList;
nodeList nodes;
nodeList::iterator listPos;
CString filePath
public:
  MyClass(CString _filePath) {
    filePath = _filePath;
    double value = 0;
    File *in = fopen(filePath,"r");
    while(!feof(in)) {
       fscanf("%f\n",value);
       nodes.push_back(value);
    }
    fclose(in)
  }
  void ~MyClass() {
    double value = 0;
    File *out = fopen(filePath,"w");
    for(listPos = nodes.begin(); listPos != nodes.end(); listPos++) {
        value = listPos;
        fprintf("%f\n",value);
    }
    fclose(out);
  }
};
I didn't do error checking so that is up to you
but I think it will lead you to what you are supposed to do.
Hope it helps,
Jens
0

Featured Post

Technology Partners: We Want Your Opinion!

We value your feedback.

Take our survey and automatically be enter to win anyone of the following:
Yeti Cooler, Amazon eGift Card, and Movie eGift Card!

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

Errors will happen. It is a fact of life for the programmer. How and when errors are detected have a great impact on quality and cost of a product. It is better to detect errors at compile time, when possible and practical. Errors that make their wa…
Article by: SunnyDark
This article's goal is to present you with an easy to use XML wrapper for C++ and also present some interesting techniques that you might use with MS C++. The reason I built this class is to ease the pain of using XML files with C++, since there is…
The goal of the tutorial is to teach the user how to use functions in C++. The video will cover how to define functions, how to call functions and how to create functions prototypes. Microsoft Visual C++ 2010 Express will be used as a text editor an…
The viewer will learn how to user default arguments when defining functions. This method of defining functions will be contrasted with the non-default-argument of defining functions.

679 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question