Is it possible to leave the type of the parameter of an interface to the receiver which implements it in Go?

Question

Basically I want to have an interface which has a SetParams method, the declaration of which declares it receives one parameter, and the return type of the method, but leaves the return type of the parameter up to the receiver.

Something like this interface:

type ParamsInterface interface {
    SetParams(<someType>) ParamsInterface
}

Now, when XStruct implements it, the type of the parameters is XParams

type XStruct struct {
    params XParams
}

func (x *XStruct) SetParams(params *XParams) ParamsInterface {
    x.params = params
    return x
}

But when YStruct implements it, the type of the parameters is YParams

type YStruct struct {
    params YParams
}

func (y *YStruct) SetParams(params *YParams) ParamsInterface {
    y.params = params
    return y
}

Anton Shkurenko · Answer 1 · 2017-11-21T10:16:46.153

0

This is called generics, you can only use empty interface interface{} and type casting.

This is doc about generics in go: https://docs.google.com/document/d/1vrAy9gMpMoS3uaVphB32uVXX4pi-HnNjkMEgyAHX4N4/edit#.

This also can help you:

How is the empty interface different than a generic?

Why no generics in Go?

This article suggests some ways how to live without generics: https://appliedgo.net/generics/

Here you can find code generator for generics (in my honest opinion that's not the best idea) https://github.com/cheekybits/genny.

edited Nov 21 '17 at 10:16

answered Nov 21 '17 at 10:00

Anton Shkurenko

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But if I use empty interface, will it won't give the autocomplete suggestions from `YParams` and `XParams` will it? – Ayush Gupta Nov 21 '17 at 10:10
@AyushGupta I updated the answer, check last two links – Anton Shkurenko Nov 21 '17 at 10:16
hmm, if I go without generics i'll have to create a Stub got a particular method for XParams – Ayush Gupta Nov 21 '17 at 10:18
@AyushGupta didn't understand you – Anton Shkurenko Nov 21 '17 at 10:25
If I do create a specific type as input , say 'CommonParams', I'll have to accept a key as input in XStruct, but not do anything with it, and use it in YStruct – Ayush Gupta Nov 21 '17 at 10:27
You can use switch and type casting for that or create CommonParams as interface with some methods, instead of struct – Anton Shkurenko Nov 21 '17 at 10:56
Let us [continue this discussion in chat](http://chat.stackoverflow.com/rooms/159473/discussion-between-anton-shkurenko-and-ayush-gupta). – Anton Shkurenko Nov 21 '17 at 11:35
2

Note that there is no type “casting” in Go. You have “type conversions” and “type assertions”, which are both quite different. – JimB Nov 21 '17 at 13:36

Is it possible to leave the type of the parameter of an interface to the receiver which implements it in Go?

1 Answers1