如何编写一个可以接受多种类型之一的函数？

Question

I'm trying go for a small project and tried to write these functions:

func fatal(reason string) {
    println(reason)
    os.Exit(1)
}

func fatal(err error) {
    fatal(err.Error())
}

After digging about a bit and finding this answer, which referenced the docs on overloading I realised that what I was trying to do was illegal in go.

What I want is a simple api that allows me to call fatal with either a string or an error in order to simplify my logic. How do I achieve this or a similar goal?

It would feel inelegant to have func fatal(reason string) along with func fatalErr(err error), is that what's needed? Am I missing a different feature of the language that allows me to do what I want?

Answer 1

The most common way to do this would be to define the method as func fatal(err interface{}) then do type assertions or use a type switch within it's body to handle each of the different types. If I were coding for your example it would look like this;

func fatal(err interface{}) {
     if v, ok := err.(string); ok {
         fmt.Println(v)
     }
     if v, ok := err.(error); ok {
          fmt.Println(v.Error())
     } else {
        // panic ?
     }
}

Also; here's a quick read about type switches and assertions that may be helpful; http://blog.denevell.org/golang-interface-type-assertions-switch.html You can also check out effective-go as it has sections on both features.