private trait that adds public methods

[Koert Kuipers]

i often have the need to factor out a few (possibly public) methods between classes in the same package.

i would like to use a trait to factor them out, but i do not want this to be visible. from the public api & scaladoc perspective i basically do not want this trait to exist.

is this possible?

[Kevin Wright]

Yes… but not as a trait.

What you describe doesn’t affect the public interface of the class, and doesn’t take part in polymorphism, so you tick exactly none of the boxes that would normally justify the use of inheritance.  Inheritance is an extremely strong and tightly-coupled mechanism which should only be used sparingly and in limited use-cases.  Anywhere else, composition is a far far better choice!

So. Move the methods into a fully-fledged class, create a private instance of this in your original class, then wildcard-import the methods from there.  Alternatively (if the helper class needs no params), you should instead move the methods into a singleton object and wildcard-import from that.

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[Koert Kuipers]

hey kevin,

thanks for responding.

the trouble is, the methods i want to factor our are public on these classes. i want to factor them out (why repeat code?), but without the factoring out being visible. so i do not want the scaladoc to be polluted with a mention of the trait/class that i factored them out to.

is this possible?

[Stephen Compall]

On October 9, 2016 11:05:04 PM EDT, Koert Kuipers <ko...@tresata.com> wrote:
>the trouble is, the methods i want to factor our are public on these
>classes. i want to factor them out (why repeat code?), but without the
>factoring out being visible. so i do not want the scaladoc to be
>polluted
>with a mention of the trait/class that i factored them out to.
>
>is this possible?

No, it's not possible. You can hide where implementations come from with enough ceremony, but not interfaces/signatures.

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Stephen Compall
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