Update versions example to use latest render subpkg

_examples/versions/main.go

@@ -1,9 +1,8 @@
 //
 // Versions
 // ========
-// This example demonstrates the use of the render subpackage and its
-// render.Presenter interface to transform a handler response to easily
-// handle API versioning.
+// This example demonstrates the use of the render subpackage, with
+// a quick concept for how to support multiple api versions.
 //
 package main
 
@@ -30,34 +29,38 @@ func main() {
 	r.Use(middleware.RequestID)
 	r.Use(middleware.Logger)
 	r.Use(middleware.Recoverer)
-	r.Use(render.UsePresenter(v3.Presenter)) // API version 3 (latest) by default.
-
-	// Redirect for Example convenience.
-	r.Get("/", func(w http.ResponseWriter, r *http.Request) {
-		http.Redirect(w, r, "/v3/articles/1", 302)
-	})
 
 	// API version 3.
 	r.Route("/v3", func(r chi.Router) {
+		r.Use(apiVersionCtx("v3"))
 		r.Mount("/articles", articleRouter())
 	})
 
 	// API version 2.
 	r.Route("/v2", func(r chi.Router) {
-		r.Use(render.UsePresenter(v2.Presenter))
+		r.Use(apiVersionCtx("v2"))
 		r.Mount("/articles", articleRouter())
 	})
 
 	// API version 1.
 	r.Route("/v1", func(r chi.Router) {
 		r.Use(randomErrorMiddleware) // Simulate random error, ie. version 1 is buggy.
-		r.Use(render.UsePresenter(v1.Presenter))
+		r.Use(apiVersionCtx("v1"))
 		r.Mount("/articles", articleRouter())
 	})
 
 	http.ListenAndServe(":3333", r)
 }
 
+func apiVersionCtx(version string) func(next http.Handler) http.Handler {
+	return func(next http.Handler) http.Handler {
+		return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+			r = r.WithContext(context.WithValue(r.Context(), "api.version", version))
+			next.ServeHTTP(w, r)
+		})
+	}
+}
+
 func articleRouter() http.Handler {
 	r := chi.NewRouter()
 	r.Get("/", listArticles)
@@ -70,17 +73,28 @@ func articleRouter() http.Handler {
 }
 
 func listArticles(w http.ResponseWriter, r *http.Request) {
-	articles := make(chan *data.Article, 5)
+	articles := make(chan render.Renderer, 5)
 
 	// Load data asynchronously into the channel (simulate slow storage):
 	go func() {
 		for i := 1; i <= 10; i++ {
-			articles <- &data.Article{
+			article := &data.Article{
 				ID:    i,
 				Title: fmt.Sprintf("Article #%v", i),
 				Data:  []string{"one", "two", "three", "four"},
 				CustomDataForAuthUsers: "secret data for auth'd users only",
 			}
+
+			apiVersion := r.Context().Value("api.version").(string)
+			switch apiVersion {
+			case "v1":
+				articles <- v1.NewArticleResponse(article)
+			case "v2":
+				articles <- v2.NewArticleResponse(article)
+			default:
+				articles <- v3.NewArticleResponse(article)
+			}
+
 			time.Sleep(100 * time.Millisecond)
 		}
 		close(articles)
@@ -114,7 +128,19 @@ func getArticle(w http.ResponseWriter, r *http.Request) {
 		return
 	}
 
-	render.Respond(w, r, article)
+	var payload render.Renderer
+
+	apiVersion := r.Context().Value("api.version").(string)
+	switch apiVersion {
+	case "v1":
+		payload = v1.NewArticleResponse(article)
+	case "v2":
+		payload = v2.NewArticleResponse(article)
+	default:
+		payload = v3.NewArticleResponse(article)
+	}
+
+	render.Render(w, r, payload)
 }
 
 func randomErrorMiddleware(next http.Handler) http.Handler {

_examples/versions/presenter/v1/article.go

@@ -1,35 +1,22 @@
 package v1
 
 import (
-	"fmt"
 	"net/http"
 
-	"github.com/pressly/chi/_examples/versions/presenter/v2"
-	"github.com/pressly/chi/render"
+	"github.com/pressly/chi/_examples/versions/data"
 )
 
 // Article presented in API version 1.
 type Article struct {
-	*v2.Article `json:",inline" xml:",inline"`
+	*data.Article
 
 	Data map[string]bool `json:"data" xml:"data"`
 }
 
-var Presenter = render.NewPresenter(ArticleV2ToV1)
-
-func init() {
-	Presenter.CopyFrom(v2.Presenter)
+func (a *Article) Render(w http.ResponseWriter, r *http.Request) error {
+	return nil
 }
 
-func ArticleV2ToV1(r *http.Request, from *v2.Article) (*Article, error) {
-	to := &Article{
-		Article: from,
-		Data:    map[string]bool{},
-	}
-	to.SelfURL = fmt.Sprintf("http://localhost:3333/v1?id=%v", from.ID)
-	to.APIVersion = "v1"
-	for _, item := range from.Data {
-		to.Data[item] = true
-	}
-	return to, nil
+func NewArticleResponse(article *data.Article) *Article {
+	return &Article{Article: article}
 }

_examples/versions/presenter/v2/article.go

@@ -4,13 +4,14 @@ import (
 	"fmt"
 	"net/http"
 
-	"github.com/pressly/chi/_examples/versions/presenter/v3"
-	"github.com/pressly/chi/render"
+	"github.com/pressly/chi/_examples/versions/data"
 )
 
 // Article presented in API version 2.
 type Article struct {
-	*v3.Article `json:",inline" xml:",inline"`
+	// *v3.Article `json:",inline" xml:",inline"`
+
+	*data.Article
 
 	// Additional fields.
 	SelfURL string `json:"self_url" xml:"self_url"`
@@ -19,17 +20,11 @@ type Article struct {
 	URL interface{} `json:"url,omitempty" xml:"url,omitempty"`
 }
 
-var Presenter = render.NewPresenter(ArticleV3ToV2)
-
-func init() {
-	Presenter.CopyFrom(v3.Presenter)
+func (a *Article) Render(w http.ResponseWriter, r *http.Request) error {
+	a.SelfURL = fmt.Sprintf("http://localhost:3333/v2?id=%v", a.ID)
+	return nil
 }
 
-func ArticleV3ToV2(r *http.Request, from *v3.Article) (*Article, error) {
-	to := &Article{
-		Article: from,
-		SelfURL: fmt.Sprintf("http://localhost:3333/v2?id=%v", from.ID),
-	}
-	to.APIVersion = "v2"
-	return to, nil
+func NewArticleResponse(article *data.Article) *Article {
+	return &Article{Article: article}
 }

_examples/versions/presenter/v3/article.go

@@ -2,14 +2,10 @@ package v3
 
 import (
 	"fmt"
-	"log"
 	"math/rand"
 	"net/http"
-	"reflect"
-	"time"
 
 	"github.com/pressly/chi/_examples/versions/data"
-	"github.com/pressly/chi/render"
 )
 
 // Article presented in API version 2.
@@ -26,84 +22,18 @@ type Article struct {
 	CustomDataForAuthUsers interface{} `json:"custom_data,omitempty" xml:"custom_data,omitempty"`
 }
 
-var Presenter = render.NewPresenter(CatchAll, ArticleToV3, ArticleChanToV3Chan, ArticleSliceToV3Slice)
+func (a *Article) Render(w http.ResponseWriter, r *http.Request) error {
+	a.ViewsCount = rand.Int63n(100000)
+	a.URL = fmt.Sprintf("http://localhost:3333/v3/?id=%v", a.ID)
 
-func ArticleToV3(r *http.Request, from *data.Article) (*Article, error) {
-	log.Printf("item presenter!")
-
-	rand.Seed(time.Now().Unix())
-	to := &Article{
-		Article:    from,
-		ViewsCount: rand.Int63n(100000),
-		URL:        fmt.Sprintf("http://localhost:3333/v3/?id=%v", from.ID),
-		APIVersion: "v3",
-	}
 	// Only show to auth'd user.
 	if _, ok := r.Context().Value("auth").(bool); ok {
-		to.CustomDataForAuthUsers = from.CustomDataForAuthUsers
-	}
-	return to, nil
-}
-
-// An optional, optimized presenter for channnel of Articles.
-// If not defined, each item will be preseted using ArticleToV3() func.
-func ArticleChanToV3Chan(r *http.Request, fromChan chan *data.Article) (chan *Article, error) {
-	log.Printf("channel presenter!")
-
-	rand.Seed(time.Now().Unix())
-
-	toChan := make(chan *Article, 5)
-	go func() {
-		for from := range fromChan {
-			to := &Article{
-				Article:    from,
-				ViewsCount: rand.Int63n(100000),
-				URL:        fmt.Sprintf("http://localhost:3333/v3/?id=%v", from.ID),
-				APIVersion: "v3",
-			}
-			// Only show to auth'd user.
-			if _, ok := r.Context().Value("auth").(bool); ok {
-				to.CustomDataForAuthUsers = from.CustomDataForAuthUsers
-			}
-
-			toChan <- to
-		}
-		close(toChan)
-	}()
-
-	return toChan, nil
-}
-
-// An optional, optimized presenter for slice of Articles.
-// If not defined, each item will be preseted using ArticleToV3() func.
-func ArticleSliceToV3Slice(r *http.Request, fromSlice []*data.Article) ([]*Article, error) {
-	log.Printf("slice presenter!")
-
-	rand.Seed(time.Now().Unix())
-
-	toSlice := make([]*Article, len(fromSlice))
-	for i, from := range fromSlice {
-		to := &Article{
-			Article:    from,
-			ViewsCount: rand.Int63n(100000),
-			URL:        fmt.Sprintf("http://localhost:3333/v3/?id=%v", from.ID),
-			APIVersion: "v3",
-		}
-		// Only show to auth'd user.
-		if _, ok := r.Context().Value("auth").(bool); ok {
-			to.CustomDataForAuthUsers = from.CustomDataForAuthUsers
-		}
-		toSlice[i] = to
+		a.CustomDataForAuthUsers = a.Article.CustomDataForAuthUsers
 	}
 
-	return toSlice, nil
+	return nil
 }
 
-func CatchAll(r *http.Request, v interface{}) (*http.Request, interface{}) {
-	if val := reflect.ValueOf(v); val.IsValid() {
-		if err, ok := val.Interface().(error); ok {
-			return data.PresentError(r, err)
-		}
-	}
-	return r, v
+func NewArticleResponse(article *data.Article) *Article {
+	return &Article{Article: article}
 }

mux_test.go

@@ -334,7 +334,6 @@ func TestMuxNestedNotFound(t *testing.T) {
 	})
 
 	sr1 := NewRouter()
-	sr1.Use()
 
 	sr1.Get("/sub", func(w http.ResponseWriter, r *http.Request) {
 		w.Write([]byte("sub"))

render/responder.go

@@ -165,12 +165,12 @@ func channelEventStream(w http.ResponseWriter, r *http.Request, v interface{}) {
 			v := recv.Interface()
 
 			// Build each channel item.
-			if renderer, ok := v.(Renderer); ok {
-				err := renderer.Render(w, r)
+			if rv, ok := v.(Renderer); ok {
+				err := renderer(w, r, rv)
 				if err != nil {
 					v = err
 				} else {
-					v = renderer
+					v = rv
 				}
 			}
 
@@ -211,12 +211,12 @@ func channelIntoSlice(w http.ResponseWriter, r *http.Request, from interface{})
 			v := recv.Interface()
 
 			// Render each channel item.
-			if renderer, ok := v.(Renderer); ok {
-				err := renderer.Render(w, r)
+			if rv, ok := v.(Renderer); ok {
+				err := renderer(w, r, rv)
 				if err != nil {
 					v = err
 				} else {
-					v = renderer
+					v = rv
 				}
 			}