using a func type instead of the Encoder interface

api.go

@@ -20,10 +20,10 @@ func GetAlbums(r *http.Request, enc Encoder, db DB) string {
 	}
 	if band != "" || title != "" || yri != 0 {
 		// At least one filter, use Find()
-		return Must(enc.Encode(toIface(db.Find(band, title, yri))...))
+		return Must(enc(toIface(db.Find(band, title, yri))...))
 	}
 	// Otherwise, return all albums
-	return Must(enc.Encode(toIface(db.GetAll())...))
+	return Must(enc(toIface(db.GetAll())...))
 }
 
 // GetAlbum returns the requested album.
@@ -32,10 +32,10 @@ func GetAlbum(enc Encoder, db DB, parms martini.Params) (int, string) {
 	al := db.Get(id)
 	if err != nil || al == nil {
 		// Invalid id, or does not exist
-		return http.StatusNotFound, Must(enc.Encode(
+		return http.StatusNotFound, Must(enc(
 			NewError(ErrCodeNotExist, fmt.Sprintf("the album with id %s does not exist", parms["id"]))))
 	}
-	return http.StatusOK, Must(enc.Encode(al))
+	return http.StatusOK, Must(enc(al))
 }
 
 // AddAlbum creates the posted album.
@@ -45,12 +45,12 @@ func AddAlbum(w http.ResponseWriter, r *http.Request, enc Encoder, db DB) (int,
 	switch err {
 	case ErrAlreadyExists:
 		// Duplicate
-		return http.StatusConflict, Must(enc.Encode(
+		return http.StatusConflict, Must(enc(
 			NewError(ErrCodeAlreadyExists, fmt.Sprintf("the album '%s' from '%s' already exists", al.Title, al.Band))))
 	case nil:
 		// TODO : Location is expected to be an absolute URI, as per the RFC2616
 		w.Header().Set("Location", fmt.Sprintf("/albums/%d", id))
-		return http.StatusCreated, Must(enc.Encode(al))
+		return http.StatusCreated, Must(enc(al))
 	default:
 		panic(err)
 	}
@@ -61,16 +61,16 @@ func UpdateAlbum(r *http.Request, enc Encoder, db DB, parms martini.Params) (int
 	al, err := getPutAlbum(r, parms)
 	if err != nil {
 		// Invalid id, 404
-		return http.StatusNotFound, Must(enc.Encode(
+		return http.StatusNotFound, Must(enc(
 			NewError(ErrCodeNotExist, fmt.Sprintf("the album with id %s does not exist", parms["id"]))))
 	}
 	err = db.Update(al)
 	switch err {
 	case ErrAlreadyExists:
-		return http.StatusConflict, Must(enc.Encode(
+		return http.StatusConflict, Must(enc(
 			NewError(ErrCodeAlreadyExists, fmt.Sprintf("the album '%s' from '%s' already exists", al.Title, al.Band))))
 	case nil:
-		return http.StatusOK, Must(enc.Encode(al))
+		return http.StatusOK, Must(enc(al))
 	default:
 		panic(err)
 	}
@@ -110,7 +110,7 @@ func DeleteAlbum(enc Encoder, db DB, parms martini.Params) (int, string) {
 	id, err := strconv.Atoi(parms["id"])
 	al := db.Get(id)
 	if err != nil || al == nil {
-		return http.StatusNotFound, Must(enc.Encode(
+		return http.StatusNotFound, Must(enc(
 			NewError(ErrCodeNotExist, fmt.Sprintf("the album with id %s does not exist", parms["id"]))))
 	}
 	db.Delete(id)

encoding.go

@@ -9,9 +9,8 @@ import (
 
 // An Encoder implements an encoding format of values to be sent as response to
 // requests on the API endpoints.
-type Encoder interface {
-	Encode(v ...interface{}) (string, error)
-}
+
+type Encoder func(v ...interface{}) (string, error)
 
 // Because `panic`s are caught by martini's Recovery handler, it can be used
 // to return server-side errors (500). Some helpful text message should probably
@@ -23,10 +22,8 @@ func Must(data string, err error) string {
 	return data
 }
 
-type jsonEncoder struct{}
-
 // jsonEncoder is an Encoder that produces JSON-formatted responses.
-func (_ jsonEncoder) Encode(v ...interface{}) (string, error) {
+var jsonEncoder Encoder = func(v ...interface{}) (string, error) {
 	var data interface{} = v
 	if v == nil {
 		// So that empty results produces `[]` and not `null`
@@ -38,10 +35,8 @@ func (_ jsonEncoder) Encode(v ...interface{}) (string, error) {
 	return string(b), err
 }
 
-type xmlEncoder struct{}
-
 // xmlEncoder is an Encoder that produces XML-formatted responses.
-func (_ xmlEncoder) Encode(v ...interface{}) (string, error) {
+var xmlEncoder Encoder = func(v ...interface{}) (string, error) {
 	var buf bytes.Buffer
 	if _, err := buf.Write([]byte(xml.Header)); err != nil {
 		return "", err
@@ -62,10 +57,8 @@ func (_ xmlEncoder) Encode(v ...interface{}) (string, error) {
 	return buf.String(), nil
 }
 
-type textEncoder struct{}
-
 // textEncoder is an Encoder that produces plain text-formatted responses.
-func (_ textEncoder) Encode(v ...interface{}) (string, error) {
+var textEncoder Encoder = func(v ...interface{}) (string, error) {
 	var buf bytes.Buffer
 	for _, v := range v {
 		if _, err := fmt.Fprintf(&buf, "%s\n", v); err != nil {

server.go

@@ -61,13 +61,13 @@ func MapEncoder(c martini.Context, w http.ResponseWriter, r *http.Request) {
 	// Inject the requested encoder
 	switch ft {
 	case ".xml":
-		c.MapTo(xmlEncoder{}, (*Encoder)(nil))
+		c.Map(xmlEncoder)
 		w.Header().Set("Content-Type", "application/xml")
 	case ".text":
-		c.MapTo(textEncoder{}, (*Encoder)(nil))
+		c.Map(textEncoder)
 		w.Header().Set("Content-Type", "text/plain; charset=utf-8")
 	default:
-		c.MapTo(jsonEncoder{}, (*Encoder)(nil))
+		c.Map(jsonEncoder)
 		w.Header().Set("Content-Type", "application/json")
 	}
 }