Effective Interfaces In Golang

In go interfaces are useful to use in functions that you want to support multiple types

To start we need to create a function

func hello() {

}

I want this function to be able to take strings, ints, and floats. How would I do this?

With an interface{} parameter

func hello(s interface{}) {

}

Now how to add handling for the types that you may find in an interface with a switch statement.

func hello(s interface{}) {
    switch s.(type) {
        case int:
            fmt.Printf("%d", s.(int))
        case float64:
            fmt.Printf("%d", s.(float64))
        case string:
            fmt.Printf("%s", s.(string))
        default:
            fmt.Printf("No handling for this type")
    }
}

This is an easy way to add handling for interface types using a switch statement.

Know that s.(type) can only be used within a switch statement.

You may notice the use of s.(int) and s.(string) This is simply telling the compiler that you would like to use the interface as a string or the interface as an int so that you can use functions that are associated with said type.

I hope that clears up some confusion about go interfaces

Comments

[Matthieu Cneude]

This is currently the only way to manage generic programming in Golang (with reflection but, I mean, be very careful with that). But generics are coming, and when it will be officially rolled out we shouldn't use this kind of code anymore.