Question

I’m writing a file processing service to parse and process different kinds of transaction files. I have a generic file parser with implementations for different types of transactions as follows.

public interface IFileParser<T> 
{
   List<T> Parse(StreamReader fileStream);
}

public MonthlyParser : IFileParser<MonthlyTransaction>
{
     public List<MonthlyTransaction> Parse(StreamReader fileStream)
     {
       ......
     }
}

public DailyParser : IFileParser<DailyTransaction>
{
     public List<DailyTransaction> Parse(StreamReader fileStream)
     {
         .....
     }
}

public enum FileTypes
{
   DailyTransaction,
   MonthlyTransaction
}

public class FileProcessor
{
    private TransactionContext dataContext;
    private IFileParser<T> fileParser;

    public FileProcessor(TransactionContext dbContext)
    {
        dataContext = dbContext;   
    }

    public void ProcessFile(string filePath, FileType fileType)
    {
       // here instantiate IFileParser based on FileType.
       // parse and process file.
    }

}

My problem is how do I create a field in the FileProcessor class of that generic interface to which a concrete implemenation can be assigned and used? Im also thinking of moving the instantiation to an IoC.

Answer 1

You have to make FileProcessor generic too, if you want to have a field of type IFileParser<T>.

However, it’s not clear why you really need to have a field of that type anyway – why can’t it be a local variable in ProcessFile? It’s also not entirely clear what you’ll do with the list even when you’ve created it… what will you do with each element?