From 16328513bfb12d96e8f33fc37f816e1441027135 Mon Sep 17 00:00:00 2001 From: Carl Johnson Date: Thu, 27 Aug 2020 13:08:44 +0000 Subject: flag: add Func Fixes #39557 Change-Id: Ida578f7484335e8c6bf927255f75377eda63b563 GitHub-Last-Rev: b97294f7669c24011e5b093179d65636512a84cd GitHub-Pull-Request: golang/go#39880 Reviewed-on: https://go-review.googlesource.com/c/go/+/240014 Reviewed-by: Russ Cox Trust: Ian Lance Taylor --- src/flag/example_func_test.go | 41 +++++++++++++++++++++++++++++++++++++++++ 1 file changed, 41 insertions(+) create mode 100644 src/flag/example_func_test.go (limited to 'src/flag/example_func_test.go') diff --git a/src/flag/example_func_test.go b/src/flag/example_func_test.go new file mode 100644 index 0000000000..7c30c5e713 --- /dev/null +++ b/src/flag/example_func_test.go @@ -0,0 +1,41 @@ +// Copyright 2020 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 ( + "errors" + "flag" + "fmt" + "net" + "os" +) + +func ExampleFunc() { + fs := flag.NewFlagSet("ExampleFunc", flag.ContinueOnError) + fs.SetOutput(os.Stdout) + var ip net.IP + fs.Func("ip", "`IP address` to parse", func(s string) error { + ip = net.ParseIP(s) + if ip == nil { + return errors.New("could not parse IP") + } + return nil + }) + fs.Parse([]string{"-ip", "127.0.0.1"}) + fmt.Printf("{ip: %v, loopback: %t}\n\n", ip, ip.IsLoopback()) + + // 256 is not a valid IPv4 component + fs.Parse([]string{"-ip", "256.0.0.1"}) + fmt.Printf("{ip: %v, loopback: %t}\n\n", ip, ip.IsLoopback()) + + // Output: + // {ip: 127.0.0.1, loopback: true} + // + // invalid value "256.0.0.1" for flag -ip: could not parse IP + // Usage of ExampleFunc: + // -ip IP address + // IP address to parse + // {ip: , loopback: false} +} -- cgit v1.3