Question

I have an object with has two properties: Text and Type.

To avoid hard-coding the Types, I put them in the database, so they can be added to in future. At the moment the types are URL, Username and ID.

However, I now want to run a Utility method to clean up the object’s Text field based on which Type the object is (e.g. add ‘http://’ if its a URL).

Is there a way to do this in the Utilities class without hard-coding the types in a switch statement/if else block.

switch (type)
{
    case 1:
        TidyUrl();
    case 2:
        TidyUsername();
    case 3:
        TidyID();
    default:
        break;
}

In this example I’m hardcoding the IDs from the database (‘Type’ table), which can never be a good thing!

Is there a better way to do this?

Answer 1

Traditionally this is handled using a common interface, and dynamically constructing a concrete implementation to do the actual work.

for example:

public interface ITidy
{
   string Tidy(string input);
}

then the implementations

public class UrlTidy : ITidy
{
    public string Tidy(string input)
    {
        // do whatever you need to the url
    }
}

And so on for the other types of tidying. Now you need a way of instantiating the right concrete class (UrlTidy, IdTidy etc) from the type you are looking at. One way to do this might be to put the class name in the database along side the type, and use reflection to instantiate the right implementation of ITidy. Another wat would be to have a Factory class which uses some other method to instantiate the right ITidy based on type.