在Golang中传递interface {}或[] interface {}

Question

With this snippet, why does it allow interface{} to pass into the function but not []interface. And what's the difference? I know what the error says (have commented it into the function), but I'm not sure what the error means.

https://play.golang.org/p/689R_5dswFX

package main

type smsSendRequest struct {
    Recipients     string `json:"recipients"`
}

// func action(pass interface{}) {
//     //works
// }

func action(pass []interface{}) {
    //cannot use data (type *smsSendRequest) as type []interface {} in argument to action
}

func main() {
    to := "15551234567"
    var data = &smsSendRequest{
        Recipients:     to,
    }
    action(data)
}

Answer 1

The type interface{} can be used as a very generic type that would allow any other type to be assigned to it.

So if a function receives interface{}, you can pass any value to it.

That is because in Go, for a type to satisfy an interface it must just implement all methods the interface declares.

Since interface{} is an empty interface, any type will satisfy it.

On the other hand, for a type to satisfy []interface{} it must be an actual slice of empty interfaces.

So if you need a generic function that can receive any value, just use interface{} as you show in your example.

Note that interface{} will allow you to pass in either value or pointer references, so you can pass in pointers or values indistinctly to that function.