SetTriggerParameters enhancment: validate interfaces

[Orion Delwaterman]

Currently SetTriggerParameters only matches types exactly. It would be great if instead of requiring the exact type, you could pass SetTriggerParameters and validateParameters used reflect.Value#Implements to validate the parameter.

[Quim Muntal]

Could you share and code snippet example with what you want to achieve?

[Orion Delwaterman]

I have a few states where I want to pass an error through a transition

errIntType := reflect.TypeOf((*error)(nil)).Elem()
sm.SetTriggerParameters(ActionReturnError, errIntType)

sm.Configure(StateFinished).
		OnEntryFrom(ActionReturnError, func(ctx context.Context, args ...interface{}) error {
			err := args[0].(error)
			r := &VolunteerResult{
				Err: err,
			}

			chResult <- r
			close(chResult)

			return nil
		})

[Orion Delwaterman]

From the example of https://pkg.go.dev/reflect#TypeOf you can then actually check if a type implements an interace:

mport (
	"fmt"
	"io"
	"os"
	"reflect"
)

func main() {
	// As interface types are only used for static typing, a
	// common idiom to find the reflection Type for an interface
	// type Foo is to use a *Foo value.
	writerType := reflect.TypeOf((*io.Writer)(nil)).Elem()

	fileType := reflect.TypeOf((*os.File)(nil))
	fmt.Println(fileType.Implements(writerType))

}

[Quim Muntal]

Implemented in #46