CODEWITHSUNDEEP
dependency-injectioninversion-of-controlconstructor-injection
sridg
sridg

Reputation: 137

Design approach - using DI in a simple application

Hi I want to check to see if I am overthinking a design issue or not. I am quite new to DI/IoC/TDD so sorry if I am making an obvious mistake.

I have a simple application that will read from a Trade log, read some XML and then save to a database.

Ideally I want to create this application using a TDD approach with DI and possibly IoC.

So I have created some code (see below). 

public interface IDataRepository
{
   void Save(object someObject);
}

public class DataRepository : IDataRepository
{
   public void Save(object someObject){}
}

Public interface ITradeXmlProcessor
{
    void ProcessXml;
}

public class TradeXmlProcessor : ITradeXmlProcessor
{
   IDataRepository iDataRepository;
   public void ProcessXml()
   {
      // Do work....
      SaveTradeData(someObject);
   }

   private void SaveTradeData(object someObject)
   {
       iDataRepository = new DataRepository();
       iDataRepository.Save(someObject));
   }
}

public class ProgramClass
{
   ITradeXmlProcessor iTradeXmlProcessor = new TradeXmlProcessor();
   iTradeXmlProcessor.ProcessXml(); 
}

Now to me the issue here is that when I go to test this code I am unable to mock the DataRepository object.

So I considered DI, which looks like : 

public class TradeXmlProcessor : ITradeXmlProcessor
{
   private IDataRepository _iDataRepository;
   public TradeXmlProcessor(IDataRepository iDataRepository)
   {
    _iDataRepository = iDataRepository;
   }

   // Use _iDataRepository in process methods.

   // ...
}

In my program class I then can pass in a IDataRepository class but is this too much? Is this the correct approach as well? I am a bit worried I might be missing something obvious?

Testability wise I am able to inject a mocked IDataRepository object into a ITradeXMLProcessor class, process it, but not save to the database which is good, but do I really need to mock such a simple operation? I cannot see the benefit I really gain from it? 

public class ProgramClass
{
   IDataRepository iDataRepository = new DataRepository();
   ITradeXmlProcessor iTradeXmlProcessor = new TradeXmlProcessor(iDataRepository);
   iTradeXmlProcessor.ProcessXml(); 
}

Upvotes: 0

Views: 49

Answers (1)

Phil Sandler
Phil Sandler

Reputation: 28016

Your approach to using DI to inject a service looks absolutely correct.

The question of whether you will get real benefit out of it is a matter of opinion, is not really a question for SO, and requires a lot more context.

Upvotes: 1

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