list_people.go

package main

import (
    "fmt"
    "io"
    "io/ioutil"
    "log"
    "os"

    "github.com/golang/protobuf/proto"

    pb "com.deer/prototest/tutorial"
)

func writePerson(w io.Writer, p *pb.Person) {
    fmt.Fprintln(w, "Person ID:", p.Id)
    fmt.Fprintln(w, "  Name:", p.Name)
    if p.Email != "" {
        fmt.Fprintln(w, "  E-mail address:", p.Email)
    }

    for _, pn := range p.Phones {
        switch pn.Type {
        case pb.Person_MOBILE:
            fmt.Fprint(w, "  Mobile phone #: ")
        case pb.Person_HOME:
            fmt.Fprint(w, "  Home phone #: ")
        case pb.Person_WORK:
            fmt.Fprint(w, "  Work phone #: ")
        }
        fmt.Fprintln(w, pn.Number)
    }
}

func listPeople(w io.Writer, book *pb.AddressBook) {
    for _, p := range book.People {
        writePerson(w, p)
    }
}

// Main reads the entire address book from a file and prints all the
// information inside.
func main() {
    if len(os.Args) != 2 {
        log.Fatalf("Usage:  %s ADDRESS_BOOK_FILE\n", os.Args[0])
    }
    fname := os.Args[1]

    // [START unmarshal_proto]
    // Read the existing address book.
    in, err := ioutil.ReadFile(fname)
    if err != nil {
        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)
    }
    // [END unmarshal_proto]

    listPeople(os.Stdout, book)
}