flag: add a Value example

Change-Id: I579cc9f4f8e5be5fd6447a99614797ab7bc53611 Reviewed-on: https://go-review.googlesource.com/120175 Run-TryBot: Ian Lance Taylor <[email protected]> TryBot-Result: Gobot Gobot <[email protected]> Reviewed-by: Ian Lance Taylor <[email protected]>
cloudflare · Jun 21, 2018 · 6c81002 · 6c81002
1 parent 4b34289
commit 6c81002
Showing 1 changed file with 44 additions and 0 deletions.
diff --git a/src/flag/example_value_test.go b/src/flag/example_value_test.go
@@ -0,0 +1,44 @@
+// Copyright 2018 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package flag_test
+
+import (
+ "flag"
+ "fmt"
+ "net/url"
+)
+
+type URLValue struct {
+ URL *url.URL
+}
+
+func (v URLValue) String() string {
+ if v.URL != nil {
+ return v.URL.String()
+ }
+ return ""
+}
+
+func (v URLValue) Set(s string) error {
+ if u, err := url.Parse(s); err != nil {
+ return err
+ } else {
+ *v.URL = *u
+ }
+ return nil
+}
+
+var u = &url.URL{}
+
+func ExampleValue() {
+ fs := flag.NewFlagSet("ExampleValue", flag.ExitOnError)
+ fs.Var(&URLValue{u}, "url", "URL to parse")
+
+ fs.Parse([]string{"-url", "https://golang.org/pkg/flag/"})
+ fmt.Printf(`{scheme: %q, host: %q, path: %q}`, u.Scheme, u.Host, u.Path)
+
+ // Output:
+ // {scheme: "https", host: "golang.org", path: "/pkg/flag/"}
+}