Object oriented design

Question

I have two csv files A and B. A is the master repository. I need to read those files, map the records of B to A and save the mapped records to another file. The class to hold records is, say Record. The class to hold the matched records is, say, RecordMatch.

class Record
{
  string Id;
  string Name;
  string Address;
  string City;
  string State;
  string Zipcode;
}

class RecordMatch
{
  string Aid;
  string AName;
  string Bid;
  string BName;
  double NameMatchPercent;
}

The mapping scenario goes thus : First, against each record of B, the records of A are filtered using state, city and then zipcode. The records of A thus filtered are then compared with the record of B. This comparison is between the name field, and is a best-match comparison using a fuzzy string algorithm. The best match is selected and saved.

The string matching algorithm will give a percentage of match. Thus, the best result out of all the matches have to be selected.

Now that I tried my best to explain the scenario, I will come to the design issue. My initial design was to make a Mapper class, which will be something as below :

class Mapper
{
  List ReadFromFile(File);
  List FilterData(FilterType);
  void Save(List);
  RecordMatch MatchRecord(Record A, Record B);
}

But looking at the design, it simply seems to be a class wrapper over some methods. I dont see any OO design in it. I also felt that the Match() belongs more to the Record class than the Mapper class.

But on another look, I saw the class as implementing something resembling to Repository pattern.

Another way I think is to keep the Mapper class, and just move the Match() method to the Record class, something like this :

class Mapper
{
  List ReadFromFile(File);
  List FilterData(FilterType);
  void Save(List);
}

class Record
{
  string id;
  string name;
  string address;
  // other fields;

  public RecordMatch Match (Record record)
  {
    // This record will compare the name field with that of the passed Record.
    // It will return RecordMatch specifyin the percent of match.
  }
}

Now I am totally confused in this simple scenario. What would ideally be a good OO design in this scenario?

Wivani · Accepted Answer

I gave this a try. There's not so much you can do when it comes to OO principles or design patterns I think, except for maybe using composition for the MatchingAlgorithm (and perhaps Strategy and Template if needed). Here's what I've cooked up:

    class Mapper {
        map(String fileA, String fileB, String fileC) {
            RecordsList a = new RecordsList(fileA);
            RecordsList b = new RecordsList(fileB);
            MatchingRecordsList c = new MatchingRecordsList();

            for(Record rb : b) {
                int highestPerc = -1;
                MatchingRecords matchingRec;

                for(Record ra : a) {
                    int perc;
                    rb.setMatchingAlgorithm(someAlgorithmYouVeDefined);
                    perc = rb.match(ra);
                    if(perc > highestPerc) {
                        matchingRec = new MatchingRecords(rb, ra, perc);
                    }
                }

                if(matchingRec != null) {
                    c.add(matchingRec);
                }
            }

            c.saveToFile(fileC);
        }
    }

    class MatchingAlgorithm {
        int match(Record b, Record a) {
            int result;
            // do your magic
            return result;
        }
    }

    class Record {
        String Id;
        String Name;
        String Address;
        String City;
        String State;
        String Zipcode;

        MatchingAlgorithm alg;

        setMatchingAlgorithm(MatchingAlgorithm alg) {
            this.alg = alg;
        }

        int match(Record r) {
            int result; -- perc of match
            // do the matching by making use of the algorithm
            result = alg.match(this, r);
            return result;
        }

    }

    class RecordsList implements List {
        RecordsList(file f) {
            //create list by reading from csv-file)
        }
    }

    class MatchingRecords {
        Record a;
        Record b;
        int matchingPerc;

        MatchingRecords(Record a, Record b, int perc) {
            this.a = a;
            this.b = b;
            this.matchingPerc = perc;
        }
    }

    class MatchingRecordsList {
        add(MatchingRecords mr) {
            //add
        }

        saveToFile(file x) {
            //save to file
        }
    }

(This is written in Notepad++ so there can be typos etc; also the proposed classes can surely benefit from a little more refactoring but I'll leave that to you if you choose to use this layout.)

Object oriented design

Answers (2)

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