Question

I have a class, ClassA that uses a client I wrote to send text messages, TextClient, to send some text messages via a call to the static method

TextClient.Send(string text, string destination)
// where destination is a phone number

However, I also have a mail client class, MailClient, which sends emails with the same signature:

MailClient.Send(string text, string destination)
// where destination is an email address

I would like to “inject” which of these clients should be used – is this possible?

(Note: I’m aware of problems that might arise when there are entirely different rules for what values destination can hold and be considered valid, but the values are fetched from someplace else, so this class doesn’t need to bother. That’s why I want to abstract this away in the first place.)

Answer 1

Basically, get rid of the static methods. Create an interface (IMessageClient) and then two implementations (TextClient and MailClient) with instance methods implementing the interface. Then you can inject the appropriate IMessageClient into the rest of the application with ease.

You certainly can use delegates to avoid creating the interface here – but I would definitely change to using interfaces instead:

• The names involved (the interface name, method name and parameter names) convey information when you’re using them
• It allows for multiple methods in the same interface
• It prevents methods which happen to have the same argument types but a completely unrelated meaning from being used accidentally