meet it

A picks the , and a says how it went.

A server answers many paths, and each route needs its own answer. A switch compares one value with several case lines and runs the first that matches, while default catches everything else. It is a tidier way to write a long else if chain.

Every reply has a status code: 200 means OK, 400 bad request, 404 not found and 405 wrong method. http.Error(w, "no such page", http.StatusNotFound) sends a status code and a short message in one go.

A web address can carry extra values after a ?, called the : /hello?name=Sam. r.URL.Query().Get("name") reads one. It gives "" when the value is missing, so check before you rely on it.

package main
import "fmt"
import "net/http"
import "net/http/httptest"
func site(w http.ResponseWriter, r *http.Request) {
	switch r.URL.Path {
	case "/hello", "/hi":
		fmt.Fprintf(w, "Hello, %s!", r.URL.Query().Get("name"))
	default:
		http.Error(w, "no such page", http.StatusNotFound)
	}
}
func main() {
	for _, target := range []string{"/hello?name=Sam", "/hi?name=Ava", "/secret"} {
		rec := httptest.NewRecorder()
		site(rec, httptest.NewRequest("GET", target, nil))
		fmt.Println(rec.Code, rec.Body.String())
	}
}

A case can list several values with commas, and Go never runs on into the next case.

guess first

Someone POSTs to the menu. What status comes back?

Guess before you run it. Wrong guesses are how you learn, and nothing is marked.

package main
import "fmt"
import "net/http"
import "net/http/httptest"
func menu(w http.ResponseWriter, r *http.Request) {
	switch r.Method {
	case "GET":
		fmt.Fprint(w, "tea, cake, toast")
	default:
		http.Error(w, "method not allowed", http.StatusMethodNotAllowed)
	}
}
func main() {
	rec := httptest.NewRecorder()
	menu(rec, httptest.NewRequest("POST", "/menu", nil))
	fmt.Println(rec.Code)
}

your turn

Your turn. Add an animal to the zoo server.

Add a route for an animal of your own: choose its path, with no spaces, and the sound it makes. Then send the pretend request to your new path.

Your code

output

press run to see what happens

fix it

The missing page says everything is fine. Fix it!

Broken code to fix

output

press run to see what happens

The message says not found, but the status code says 200, which means OK. What sets the status?
fmt.Fprint only writes the body. http.Error sends a status code and a message together.
Change line 7 to http.Error(w, "page not found", http.StatusNotFound), then run.

nailed it

your server knows every route. :D

A switch runs the first case that matches, or default.
Status codes say how it went: 200 OK, 404 not found.
r.URL.Query().Get reads a value from the query string.

new words in your collection

route
switch
status code
query string

This lesson isn’t saved. A free account remembers every lesson you finish.

A switch picks the route, and a status code says how it went.

Someone POSTs to the menu. What status comes back?

Your turn. Add an animal to the zoo server.

The missing page says everything is fine. Fix it!

your server knows every route. :D

A picks the , and a says how it went.