I'm trying to write a function that returns the underlying reflect.Value within empty interface{} by providing the underlying type using reflect.Type:
// code in: https://play.golang.org/p/p6NLm18LjzM
package main
import (
"fmt"
"reflect"
)
type MyInt struct{
x int
}
func getUnderlyingAsValue( data interface{}, underlyingType reflect.Type) reflect.Value{
underlyingData := data.(underlyingType) // <-- Doesn't compile "underlyingType is not a type"
return reflect.ValueOf(underlyingData)
}
func main() {
var i int
i = 5
myInt := &MyInt{x:i}
underVal := getUnderlyingAsValue(myInt, reflect.TypeOf(i))
if underVal.Type() != reflect.TypeOf(myInt){
fmt.Printf("Doesn't Work! :-(")
} else {
fmt.Printf("SUCCESS!")
}
}
As written within the code, type assertion doesn't work because "reflect.Type" is not a type.
Does anyone have any idea how to solve it? Preferably without going into uintptr in the underlying structure of an interface (if there is such a way).
Thanks!
Go is a statically typed language, you can't type assert to "dynamic types".
But you don't have to. "Wrapping" any concrete value available in an interface{}
value requires no magic, just pass that as-is to reflect.ValueOf()
:
func getUnderlyingAsValue(data interface{}, underlyingType reflect.Type) reflect.Value {
return reflect.ValueOf(data)
}
Or simply:
func getUnderlyingAsValue(data interface{}) reflect.Value {
return reflect.ValueOf(data)
}
(This function isn't even justified to exist anymore, it's so simple..)
Try it on the Go Playground.
There is no point type-asserting a concrete type from an interface{}
when the next and only operation you do is pass it to a function that expects interface{}
. It would again be wrapped in an interface{}
.