go 56 lines · 8 steps

Rendering HTML pages with Gin handlers

Two Gin handlers fetch data through a repository and render templates, with graceful error pages when something fails.

Explained by highlit

Gin Beginner http-handlers templating error-handling dependency-injection type-assertion

1package handlers
2 
3import (
4	"net/http"
5	"time"
6 
7	"github.com/gin-gonic/gin"
8)
9 
10type ArticleHandler struct {
11	Articles ArticleRepository
12}
13 
14func (h *ArticleHandler) Index(c *gin.Context) {
15	articles, err := h.Articles.Recent(c.Request.Context(), 20)
16	if err != nil {
17		c.HTML(http.StatusInternalServerError, "error.tmpl", gin.H{
18			"title":   "Something went wrong",
19			"message": "We couldn't load the articles right now.",
20		})
21		return
22	}
23 
24	c.HTML(http.StatusOK, "articles/index.tmpl", gin.H{
25		"title":    "Latest Articles",
26		"articles": articles,
27		"year":     time.Now().Year(),
28		"flash":    flashFrom(c),
29	})
30}
31 
32func (h *ArticleHandler) Show(c *gin.Context) {
33	article, err := h.Articles.BySlug(c.Request.Context(), c.Param("slug"))
34	if err != nil {
35		c.HTML(http.StatusNotFound, "error.tmpl", gin.H{
36			"title":   "Not found",
37			"message": "That article has wandered off.",
38		})
39		return
40	}
41 
42	c.HTML(http.StatusOK, "articles/show.tmpl", gin.H{
43		"title":   article.Title,
44		"article": article,
45		"year":    time.Now().Year(),
46	})
47}
48 
49func flashFrom(c *gin.Context) string {
50	if v, ok := c.Get("flash"); ok {
51		if s, ok := v.(string); ok {
52			return s
53		}
54	}
55	return ""
56}

01 / 01

STEP 01

Walkthrough

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Three takeaways

1Holding a repository on the handler struct keeps data access injectable and testable instead of hard-wired.
2Checking the error before rendering lets each failure return its own status code and friendly page.
3A small helper that type-asserts context values isolates fragile lookups so handlers stay readable.

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