From 7e31c4d930efa3f80d0f03c93e788ba73b847fd8 Mon Sep 17 00:00:00 2001
From: Tim Swast <swast@google.com>
Date: Fri, 20 Nov 2015 15:32:53 -0800
Subject: Add a Go language example.

This follows the other examples so that it can be used as a tutorial,
such as the ones at:
  https://developers.google.com/protocol-buffers/docs/tutorials

Even though Go generally does not use Makefiles, I added targets for the
Go examples to be consistent with the other languages.

Edit:

Fix Travis run. Change to use $HOME instead of ~. Add protoc to path.
GOPATH entry cannot start with shell metacharacter '~': "~/gocode"

Edit(2):

Fix Go code style to address comments.
---
 examples/add_person.go | 128 +++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 128 insertions(+)
 create mode 100644 examples/add_person.go

(limited to 'examples/add_person.go')

diff --git a/examples/add_person.go b/examples/add_person.go
new file mode 100644
index 00000000..6b2d3d69
--- /dev/null
+++ b/examples/add_person.go
@@ -0,0 +1,128 @@
+package main
+
+import (
+	"bufio"
+	"fmt"
+	"io"
+	"io/ioutil"
+	"log"
+	"os"
+	"strings"
+
+	"github.com/golang/protobuf/proto"
+	pb "github.com/google/protobuf/examples/tutorial"
+)
+
+func promptForAddress(r io.Reader) (*pb.Person, error) {
+	// A protocol buffer can be created like any struct.
+	p := &pb.Person{}
+
+	rd := bufio.NewReader(r)
+	fmt.Print("Enter person ID number: ")
+	// An int32 field in the .proto file is represented as an int32 field
+	// in the generated Go struct.
+	if _, err := fmt.Fscanf(rd, "%d\n", &p.Id); err != nil {
+		return p, err
+	}
+
+	fmt.Print("Enter name: ")
+	name, err := rd.ReadString('\n')
+	if err != nil {
+		return p, err
+	}
+	// A string field in the .proto file results in a string field in Go.
+	// We trim the whitespace because rd.ReadString includes the trailing
+	// newline character in its output.
+	p.Name = strings.TrimSpace(name)
+
+	fmt.Print("Enter email address (blank for none): ")
+	email, err := rd.ReadString('\n')
+	if err != nil {
+		return p, err
+	}
+	p.Email = strings.TrimSpace(email)
+
+	for {
+		fmt.Print("Enter a phone number (or leave blank to finish): ")
+		phone, err := rd.ReadString('\n')
+		if err != nil {
+			return p, err
+		}
+		phone = strings.TrimSpace(phone)
+		if phone == "" {
+			break
+		}
+		// The PhoneNumber message type is nested within the Person
+		// message in the .proto file.  This results in a Go struct
+		// named using the name of the parent prefixed to the name of
+		// the nested message.  Just as with pb.Person, it can be
+		// created like any other struct.
+		pn := &pb.Person_PhoneNumber{
+			Number: phone,
+		}
+
+		fmt.Print("Is this a mobile, home, or work phone? ")
+		ptype, err := rd.ReadString('\n')
+		if err != nil {
+			return p, err
+		}
+		ptype = strings.TrimSpace(ptype)
+
+		// A proto enum results in a Go constant for each enum value.
+		switch ptype {
+		case "mobile":
+			pn.Type = pb.Person_MOBILE
+		case "home":
+			pn.Type = pb.Person_HOME
+		case "work":
+			pn.Type = pb.Person_WORK
+		default:
+			fmt.Printf("Unknown phone type %q.  Using default.\n", ptype)
+		}
+
+		// A repeated proto field maps to a slice field in Go.  We can
+		// append to it like any other slice.
+		p.Phones = append(p.Phones, pn)
+	}
+
+	return p, nil
+}
+
+// Main reads the entire address book from a file, adds one person based on
+// user input, then writes it back out to the same file.
+func main() {
+	if len(os.Args) != 2 {
+		log.Fatalf("Usage:  %s ADDRESS_BOOK_FILE\n", os.Args[0])
+	}
+	fname := os.Args[1]
+
+	// Read the existing address book.
+	in, err := ioutil.ReadFile(fname)
+	if err != nil {
+		if os.IsNotExist(err) {
+			fmt.Printf("%s: File not found.  Creating new file.\n", fname)
+		} else {
+			log.Fatalln("Error reading file:", err)
+		}
+	}
+	book := &pb.AddressBook{}
+	if err := proto.Unmarshal(in, book); err != nil {
+		log.Fatalln("Failed to parse address book:", err)
+	}
+
+	// Add an address.
+	addr, err := promptForAddress(os.Stdin)
+	if err != nil {
+		log.Fatalln("Error with address:", err)
+	}
+	book.People = append(book.People, addr)
+
+	// Write the new address book back to disk.
+	out, err := proto.Marshal(book)
+	if err != nil {
+		log.Fatalln("Failed to encode address book:", err)
+	}
+	if err := ioutil.WriteFile(fname, out, 0644); err != nil {
+		log.Fatalln("Failed to write address book:", err)
+	}
+}
-- 
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