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Editorial Team
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Asked: 2026-06-06T09:37:43+00:00

I work on developing an external API. I added a method to my public

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I work on developing an external API. I added a method to my public interface :

public void AddMode(TypeA mode);
public void AddMode(TypeB mode); // the new method, TypeB and TypeA are not related at all

It looked good, until one test broke that was passing a null . That made the compiler confused with ambiguous call. I fixed the test with casting the null.

However my question is :

  • Should I change the name just because of this?
  • Or should let the client do the cast as I did? (if they pass null for whatever reason)

What is the best in this case while designing APIs ?

Edit :

the call was like this AddMode(null) , not like :

TypeA vl = null; 
AddMode(v1); // this doesn't cause a problem
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1 Answer

  1. Editorial Team

    An API should be designed so that it’s easy to use correctly and hard to use incorrectly.
    Your API is easy to use correctly:

    AddMode(new TypeA());

    does compile.

    It’s harder to use incorrectly:

    AddMode(null);

    does not compile. The user ist forced to do something like

    AddMode((TypeA)null);

    Which should make him think, whether this is expected usage. So I think your API is OK as it is.

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