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goembedding

Accessing embedded methods in GoLang


I'm trying to create some generic functions in go that handle lots of different object types, some of the types embed a handy sub type I've created call BaseObject.

I can't seem to figure out how to test if 'Value interface{}' contains a BaseObject, or how to then call one of it's methods e.g. ToString()... which should return [TestObject] not [BaseObject]

package Test

import(
    "fmt"
    "reflect"
)

func main() {
    Value:=TestObject{}
    TestFunction(Value)
}

//Generic function
func TestFunction(Value interface{}){

    // Does value contain BaseObject? reflect.TypeOf(Value).Containes...Implements??
    //Convert to BaseObject? BO:=Value.(BaseObject)
    // If it does, call BO.ToString()
    //fmt.println(BO.ToString())
}

//Base Object
type BaseObject struct {
}
func (this *HCObject) ToString() string {
    return "[BaseObject]"
}

//Test Object
type TestObject struct{
    BaseObject
}
func (this *TestObject) ToString() string {
    return "[TestObject]"
}

Solution

  • First of all, a couple of points:

    • It is a good practice to give links to working code examples at play.golang.org.
    • Always fmt your code.
    • ToString should be String. See fmt.Stringer interface.
    • As others have pointed out, trying to write Java of C++ in Go will end with a log of pain below the back.

    With that said, this is a runnable example of the code that does what you want with many buts.

    func TestFunction(v interface{}) {
        fmt.Println(reflect.ValueOf(v).FieldByName("BaseObject").MethodByName("String").Call(nil)[0].String())
    }
    

    This code uses the reflect package (which is something you should do only when you really need it). I suggest you play with that example and dig into reflect to see, whether it's worth it to continue the way you go with Go.