Generic variadic argument in Go?

Question

I know that Go doesn't support templates or overloaded functions, but I'm wondering if there's any way to do some kind of generic programming for variadic functions anyway?

I have many functions such as these:

func (this Document) GetString(name string, defaults ...string) string {
    v, ok := this.GetValueFromDb(name)
    if !ok {
        if len(defaults) >= 1 {
            return defaults[0]
        } else {
            return ""
        }
    }
    return v.asString
}

func (this Document) GetInt(name string, defaults ...int) int {
    v, ok := this.GetValueFromDb(name)
    if !ok {
        if len(defaults) >= 1 {
            return defaults[0]
        } else {
            return 0
        }
    }
    return v.asInt
}

// etc. for many different types

Is there any way to do this without having so much redundant code?

Answer 1

The most of what you can achieve is usage of interface{} type, something like this:

func (this Document) Get(name string, defaults ...interface{}) interface{} {
    v, ok := this.GetValueFromDb(name)
    if !ok {
        if len(defaults) >= 1 {
            return defaults[0]
        } else {
            return 0
        }
    }
    return v
}

GetValueFromDb function should also be tweaked to return interface{} value and not some wrapper like now.

Then in the client code you can do the following:

value := document.Get("index", 1).(int)  // Panics when the value is not int

or

value, ok := document.Get("index", 1).(int)  // ok is false if the value is not int

This will yield some runtime overhead though. I'd better stick with separate functions and try to restructure the code somehow.