I am facing a problem with dependency inversion in a factory
method and it is also breaking Open Closed principle. My code looks like below codes
public interface IWriter
{
void WriteToStorage(string data);
}
public class FileWriter : IWriter
{
public void WriteToStorage(string data)
{
//write to file
}
}
public class DBWriter : IWriter
{
public void WriteToStorage(string data)
{
//write to DB
}
}
Now I an using a factory class to solve the object creation. It look like below code
public interface IFactory
{
IWriter GetType(string outputType);
}
public class Factory : IFactory
{
public IWriter GetType(string outputType)
{
IWriter writer = null;
if (outputType.Equels("db"))
{
writer = new FileWriter();
}
else if (outputType.Equels("db"))
{
writer = new DBWriter();
}
}
}
Now the problem is the Factory
class is breaking Open closed principle so it also breakes Dependency Inversion Principle
And then
public interface ISaveDataFlow
{
void SaveData(string data, string outputType);
}
public class SaveDataFlow : ISaveDataFlow
{
private IFactory _writerFactory = null;
public SaveDataFlow(IFactory writerFactory)
{
_writerFactory = writerFactory;
}
public void SaveData(string data, string outputType)
{
IWriter writer = _writerFactory.GetType(outputType);
writer.WriteToStorage(data);
}
}
As the above factory class is breaking the dependency inversion I remove the Factory
class and change the SaveDataFlow
class like below
public class SaveDataFlow : ISaveDataFlow
{
private IWriter _dbWriter = null;
private IWriter _fileWriter = null;
public SaveDataFlow([Dependency("DB")]IWriter dbWriter,
[Dependency("FILE")]IWriter fileWriter)
{
_dbWriter = dbWriter;
_fileWriter = fileWriter;
}
public void SaveData(string data, string outputType)
{
if (outputType.Equals("DB"))
{
_dbWriter.WriteToStorage(data);
}
else if (outputType.Equals("FILE"))
{
_fileWriter.WriteToStorage(data);
}
}
}
And resolved those dependencies using Unity Framework
container.RegisterType<IWriter, DBWriter>("DB");
container.RegisterType<IWriter, FileWriter>("FILE");
Yet eventually I am ending up breaking Open Closed Principle.
I need a better design/solution to solve such a problem yet I must follow SOLID Principles.
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