Not sure with my approach in .net application

Question

once again I'm here for help. I'm writing my first "real-like" application to practice what I learned and I am not sure about my approach. I'll try to explain it as best as my english allows me.

Application consist of base abstract class and three classes inherited from that base.

abstract class BaseClass
{
     // Some stuff...

     // This method is used in all classes. It gets whole adb output
     // and returns it as a string for future formating
    protected string ProcessAdbCommand(string command)
    {
        try
        {
            _processInfo.Arguments = command;
            Process adbProcess = Process.Start(_processInfo);
            adbProcess.WaitForExit();
            return adbProcess.StandardOutput.ReadToEnd();
        }
        catch (Exception e)
        {
            WriteToLog(e.Message);
            return null;
        }            
    } 
}

After ProcessAdbCommand returns output, I will call another method which handles output as needed. Principle is always the same - format output and make somethinkg usefull based on the output.

Now I'd like to make clear, that method responsible for output handling needs to be in every inherited class. But problem is that in very class it returns different value type (boolean, List of IDevice and strings)

I am struggling here. First I wanted to make it protected abstract. Somethink like

abstract class BaseClass
{
     // Some stuff...

    // Same as above
    protected string ProcessAdbCommand(string command)
    {
            //Same as above
    }

    //Method which will be implemented in every inherited class differently
    protected bool|List<IDevice>|string ProcessAdbOutput(string adbOutput)
    {
            //Method implementation

            return bool|List<IDevice>|string
    } 
}

But as I discovered it is not possible to override return type. And because method will be always used only internally in classes, I do not see reason to "force" it using interfaces.

After some time I game up and decided to forget about forcing implementation in derived classes and simply write them as I need. But do you think it is "legal" approach? How would you solve problem like that in "real world" application? Is there something I am still missing or is my approach simply wrong? Thank you.

Struggling Greenhorn.

First, an abstract class needs to be inherited, it can't be instantiated on it's own. Secondly, to make this work you'll need to have 3 methods in your abstract class (one for each of the return types). You *might* be able to use a generic method in the abstract class, but without researching it I don't know if that would actually work (I kind of think it wouldn't). — Tim, Sep 12 '15 at 17:05

Yuval Itzchakov · Answer 1 · 2015-09-12T17:55:56.247

One possible approach would be to make the abstract base class generic and accept a T parameter, which can also be the output of your ProcessAdbOutput method. Then, you make the method abstract to make sure any derived type has to implement it:

public abstract class BaseClass<T>
{
    protected string ProcessAdbCommand(string command)
    {
        return string.Empty;
    }

    public abstract T ProcessAdbOutput(string result);
}

public class DerivedClass : BaseClass<IList<IDevice>>
{
    public override IList<IDevice> ProcessAdbOutput(string result)
    {
        return new List<IDevice>();
    }
}

Not sure with my approach in .net application

1 Answers1