custom type for arguments in order to have convenient cast methods

cmd/godog/main.go

@@ -19,6 +19,7 @@ func main() {
 	builtFile := fmt.Sprintf("%s/%dgodog.go", os.TempDir(), time.Now().UnixNano())
 	defer os.Remove(builtFile) // comment out for debug
 
+	// @TODO: handle multiple init functions
 	buf, err := godog.Build()
 	if err != nil {
 		panic(err)

gherkin/example/ls_test.go

@@ -1,16 +1,28 @@
 package main
 
 import (
-	"log"
 	"regexp"
 
 	"github.com/DATA-DOG/godog"
 )
 
-func SomeContext(g godog.Suite) {
+type lsFeature struct{}
-	f := godog.StepHandlerFunc(func(args ...interface{}) error {
+
-		log.Println("step triggered")
+func (s *lsFeature) inDirectory(args ...godog.Arg) error {
 	return nil
-	})
+}
-	g.Step(regexp.MustCompile("hello"), f)
+
+func (s *lsFeature) haveFile(args ...godog.Arg) error {
+	return nil
+}
+
+func SuiteContext(g godog.Suite) {
+	f := &lsFeature{}
+
+	g.Step(
+		regexp.MustCompile(`^I am in a directory "([^"]*)"$`),
+		godog.StepHandlerFunc(f.inDirectory))
+	g.Step(
+		regexp.MustCompile(`^I have a file named "([^"]*)"$`),
+		godog.StepHandlerFunc(f.haveFile))
 }

suite.go

@@ -4,10 +4,25 @@ import (
 	"flag"
 	"fmt"
 	"regexp"
+	"strconv"
 
 	"github.com/DATA-DOG/godog/gherkin"
 )
 
+// Arg is an argument for StepHandler parsed from
+// the regexp submatch to handle the step
+type Arg string
+
+// Float converts an argument to float64 value
+// or panics if it does not know how to convert it
+func (a Arg) Float() float64 {
+	v, err := strconv.ParseFloat(string(a), 64)
+	if err == nil {
+		return v
+	}
+	panic(fmt.Sprintf(`cannot convert string "%s" to float64: %s`, a, err))
+}
+
 // Objects implementing the StepHandler interface can be
 // registered as step definitions in godog
 //
@@ -20,17 +35,17 @@ import (
 // and that the feature runner can move on to the next
 // step.
 type StepHandler interface {
-	HandleStep(args ...interface{}) error
+	HandleStep(args ...Arg) error
 }
 
 // StepHandlerFunc type is an adapter to allow the use of
 // ordinary functions as Step handlers.  If f is a function
 // with the appropriate signature, StepHandlerFunc(f) is a
 // StepHandler object that calls f.
-type StepHandlerFunc func(...interface{}) error
+type StepHandlerFunc func(...Arg) error
 
 // HandleStep calls f(step_arguments...).
-func (f StepHandlerFunc) HandleStep(args ...interface{}) error {
+func (f StepHandlerFunc) HandleStep(args ...Arg) error {
 	return f(args...)
 }