How to determine an interface{} value's “real” type?

Question

I have not found a good resource for using interface{} types. For example

package main

import \"fmt\"

func weirdFunc(i int) interface{} {
             


        

Answer 1

Your example does work. Here's a simplified version.

package main

import "fmt"

func weird(i int) interface{} {
    if i < 0 {
        return "negative"
    }
    return i
}

func main() {
    var i = 42
    if w, ok := weird(7).(int); ok {
        i += w
    }
    if w, ok := weird(-100).(int); ok {
        i += w
    }
    fmt.Println("i =", i)
}

Output:
i = 49

It uses Type assertions.