golang开发实践

先处理错误避免嵌套

尽量避免重复

重复的代码想办法用一个函数包起来

type binWriter struct {
    w    io.Writer
    size int64
    err  error
}

// Write writes a value to the provided writer in little endian form.
func (w *binWriter) Write(v interface{}) {
    if w.err != nil {
        return
    }
    if w.err = binary.Write(w.w, binary.LittleEndian, v); w.err == nil {
        w.size += int64(binary.Size(v))
    }
}

func (g *Gopher) WriteTo(w io.Writer) (int64, error) {
    bw := &binWriter{w: w}
    bw.Write(int32(len(g.Name)))
    bw.Write([]byte(g.Name))
    bw.Write(int64(g.AgeYears))
    return bw.size, bw.err
}

也可以通过type-switch处理不同类型(可以利用在配置表差不多有相同字段)

func (w *binWriter) Write(v interface{}) {
    if w.err != nil {
        return
    }
    switch v.(type) {
    case string:
        s := v.(string)
        w.Write(int32(len(s)))
        w.Write([]byte(s))
    case int:
        i := v.(int)
        w.Write(int64(i))
    default:
        if w.err = binary.Write(w.w, binary.LittleEndian, v); w.err == nil {
            w.size += int64(binary.Size(v))
        }
    }
}

func (g *Gopher) WriteTo(w io.Writer) (int64, error) {
    bw := &binWriter{w: w}
    bw.Write(g.Name)
    bw.Write(g.AgeYears)
    return bw.size, bw.err
}

函数适配器

函数 handler 包含了业务的逻辑和错误处理，下来将错误处理单独写一个函数处理

func init() {
    http.HandleFunc("/", errorHandler(betterHandler))
}

func errorHandler(f func(http.ResponseWriter, *http.Request) error) http.HandlerFunc {
    return func(w http.ResponseWriter, r *http.Request) {
        err := f(w, r)
        if err != nil {
            http.Error(w, err.Error(), http.StatusInternalServerError)
            log.Printf("handling %q: %v", r.RequestURI, err)
        }
    }
}

func betterHandler(w http.ResponseWriter, r *http.Request) error {
    if err := doThis(); err != nil {
        return fmt.Errorf("doing this: %v", err)
    }

    if err := doThat(); err != nil {
        return fmt.Errorf("doing that: %v", err)
    }
    return nil
}

先写最重要的代码

查询文档

go install golang.org/x/tools/cmd/godoc@latest

godoc -http=:6060

 

给代码写文档注释

命名尽可能简洁

保持包的独立性

如果一个包对另一个包有强依赖性的时候，例如下列的parse，draw

// Parse the text into an executable function.
  f, err := parser.Parse(text)
  if err != nil {
      log.Fatalf("parse %q: %v", text, err)
  }

  // Create an image plotting the function.
  m := drawer.Draw(f, *width, *height, *xmin, *xmax)

  // Encode the image into the standard output.
  err = png.Encode(os.Stdout, m)
  if err != nil {
      log.Fatalf("encode image: %v", err)
  }

代码中 Draw 方法接受了 Parse 函数返回的 f 变量，从逻辑上看 drawer 包依赖 parser 包

parser 包：

type ParsedFunc struct {
    text string
    eval func(float64) float64
}

func Parse(text string) (*ParsedFunc, error) {
    f, err := parse(text)
    if err != nil {
        return nil, err
    }
    return &ParsedFunc{text: text, eval: f}, nil
}

func (f *ParsedFunc) Eval(x float64) float64 { return f.eval(x) }
func (f *ParsedFunc) String() string         { return f.text }

import "image"

// Function represent a drawable mathematical function.
type Function interface {
    Eval(float64) float64
}

// Draw draws an image showing a rendering of the passed Function.
func Draw(f Function) image.Image {

用接口解耦

避免内部的并发

函数do暴露给对外，内部自己处理并发

func do(job string) error {
    fmt.Println("doing job", job)
    time.Sleep(1 * time.Second)
    return errors.New("something went wrong!")
}

func main() {
    jobs := []string{"one", "two", "three"}

    errc := make(chan error)
    for _, job := range jobs {
        go func(job string) {
            errc <- do(job)
        }(job)
    }
    for _ = range jobs {
        if err := <-errc; err != nil {
            fmt.Println(err)
        }
    }
}

创建一个传递退出状态的通道来避免Goroutine的泄露

func broadcastMsg(msg string, addrs []string) error {
    errc := make(chan error)
    quit := make(chan struct{})

    defer close(quit)

    for _, addr := range addrs {
        go func(addr string) {
            select {
            case errc <- sendMsg(msg, addr):
                fmt.Println("done")
            case <-quit:
                fmt.Println("quit")
            }
        }(addr)
    }

    for _ = range addrs {
        if err := <-errc; err != nil {
            return err
        }
    }
    return nil
}