CODEWITHSUNDEEP
c#design-patterns
Daryl
Daryl

Reputation: 18895

Is This a Software Design Pattern?

Assuming you start out with these two classes:

public class Foo{   
    public virtual Baz Bar(){
        return GetStandardBaz();
    }
}

public class Qux: Foo{
    public virtual Baz Bar(){
        return GetQuxBaz();
    }
}

Now lets say a requirement comes up to do something with Baz before returning it when Bar gets called. I would create a virtual protected method, and remove the virtual from the public method like so:

public class Foo{   
    public Baz Bar(){
        var value = BarInternal();
        DoSomethingFirst(value);
        return value;
    }

    protected virtual Baz BarInternal(){
        return GetStandardBaz();
    }
}

public class Qux: Foo{
    protected override Baz BarInternal(){
        return GetQuxBaz();
    }
}

This ensures that whenever Bar get's called, the resultant Baz is passed into DoSomethingFirst before being returned. Yes this is a breaking change for all child classes, but it doesn't require any updates to any call sites of Bar.

Is this a standard design pattern? Is there a better way that I'm missing? Also wondering if there is a better post-fix name than Internal.

Upvotes: 3

Views: 163

Answers (2)

Oleksandr Kobylianskyi
Oleksandr Kobylianskyi

Reputation: 3370

If you slightly change Foo class as follows you will get Template Method pattern.

public class Foo{   
    public Baz Bar(){
        var value = BarInternal();
        DoSomethingFirst(value);
        return value;
    }

    protected virtual Baz BarInternal(){
        return GetStandardBaz();
    }
}

You can achieve something similar with Decorator pattern as well. Decision will depend on details of what your classes are intended to do.

Upvotes: 2

usr
usr

Reputation: 171178

This is a good thing because you can filter the inputs and outputs in a standard way. You can do validation and additional processing.

You can also validate inputs so that the inner/virtual method can rely on certain conditions to be true.

I usually use the suffix "Core" (GetBarCore).

Upvotes: 1

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