I have a Result interface which represents the minimum state of a result. Now there are different structs which implement the Result interface but also add own methods. One of them is SpecialResult which implemented the basic Value() method but also a special Special() method.
You can see this in the following snippet:
package main
import (
"fmt"
"reflect"
)
type Result interface {
Value() string
}
type SpecialResult struct {
value string
}
func (r *SpecialResult) Value() string {
return r.value
}
func (r *SpecialResult) Special() string {
return "look I am special!!"
}
func main() {
sr := &SpecialResult{
value: "1234",
}
doSomething(sr)
}
func doSomething(r Result) {
switch reflect.TypeOf(r).String() {
case "*main.SpecialResult":
fmt.Printf("%s, %s
", r.Value(), r.(*SpecialResult).Special())
break
default:
fmt.Printf("%s
", r.Value())
}
}
When you read the last lines of code you might feel the same as I do: This looks very weird.
Is there a better way to achieve the shown setup?
Bodo
Use Type Assertions
package main
import (
"fmt"
)
type Result interface {
Value() string
}
type SpecialResult struct {
value string
}
func (r *SpecialResult) Value() string {
return r.value
}
func (r *SpecialResult) Special() string {
return "look I am special!!"
}
func main() {
sr := &SpecialResult{
value: "1234",
}
doSomething(sr)
}
func doSomething(r Result) {
if special, ok := r.(*SpecialResult); ok {
fmt.Printf("%s, %s
", special.Value(), special.Special())
} else {
fmt.Printf("%s
", r.Value())
}
}