I am trying to see if Go supports a language feature I use in other OO languages (such as Java). I'd like to define a few interfaces and pass an object that supports some of them to a function as a parameter.

In Java I might define a bunch of single method interfaces like HasAdd, HadMul, HasSub, HasDiv, HasSin, HasCos, HasTan, etc.

And then I might define a generic method whose argument T is defined as <T extends HasSin & HasAdd>. I pass in a T to the method. Note I don't have to define an intermediate Interface that contains both HasSin and HasAdd. (Which is great because n interfaces results in needing 2^n intermediate interfaces to cover all cases).

I know go does not support generics. But can it do something like func(HasSin & HasAdd obj)? It seems it should support this behavior. I just haven't found documentation that cinches it either way.

I have seen this: https://golangbot.com/interfaces-part-2/ where there is an example of something similar near the bottom of the article but it does indeed use an intermediate interface.

1 Answers

6
ThunderCat On Best Solutions

Declare an interface with the methods required by the function:

type SinAdder interface {
    Sin(float64) float64
    Add(float64, float64) float64
}

If you declared the single method interfaces Siner and Adder, then you can declare SinAdder in terms of those interfaces:

type SinAdder interface {
    Siner
    Adder
}

Use that interface in the function:

func example(arg SinAdder) {
}

Any value that has the Sin and Add methods can be passed to example.

You can void declaring the SinAdder interface by using an anonymous interface definition in the function argument:

func example(arg interface { Siner; Adder }) {
}