How Can I Access Keys from Go Maps with Different Value Types?

Accessing Keys of Maps with Different Value Types

In Go, maps are inherently generic, but their behavior is not covariant due to the absence of generic types. This means that you may encounter scenarios where you wish to access keys of maps with different value types. An attempt to use an interface{} as the value type may seem intuitive, but it doesn't work as expected.

func main() {
    mapOne := map[string]int
    mapTwo := map[string]double
    mapThree := map[string]SomeStruct

    useKeys(mapOne)
}
func useKeys(m map[string]interface{}) {
    //something with keys here
}

While it's understandable to desire an elegant solution, it's necessary to acknowledge that in Go, you may need to replicate certain logic for maps with different value types.

However, if you require the flexibility to obtain keys from any map, reflection can be employed:

func useKeys(m interface{}) {
    v := reflect.ValueOf(m)
    if v.Kind() != reflect.Map {
        fmt.Println("not a map!")
        return
    }

    keys := v.MapKeys()
    fmt.Println(keys)
}

This approach allows you to work with maps of any type, providing access to their keys.

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