3-1 defer调用.mp4

  1. func writeFile(filename string){
  2.     file,err:=os.Create(filename)
  3.     if err != nil {
  4.         panic(err)
  5.     }
  6.     defer file.Close()
  7.     writer:= bufio.NewWriter(file)
  8.     defer writer.Flush()
  9.     for i := 0; i < 20; i++ {
  10.         fmt.Fprintln(writer,string(i))
  11.     }
  12. }

等我代码写完了,我就忘记这个了
所以我就进就加一个这个
第3章_错误处理和资源管理 - 图1

  1. package main
  2. import (
  3.     "bufio"
  4.     "fmt"
  5.     "os"
  6. )
  7. func tryDefer() {
  8.     defer fmt.Println(2)
  9.     defer fmt.Println(1)
  10.     fmt.Println(3)
  11.     fmt.Println(4)
  12. }
  13. func writeFile(filename string) {
  14.     file, err := os.Create(filename)
  15.     if err != nil {
  16.         panic(err)
  17.     }
  18.     defer file.Close()
  19.     writer := bufio.NewWriter(file)
  20.     defer writer.Flush()
  21.     for i := 0; i < 20; i++ {
  22.         fmt.Fprintln(writer, i)
  23.     }
  24. }
  25. func main() {
  26.     writeFile("fib.txt")
  27. }

3-2 错误处理概念.mp4

  1. package main
  2. import (
  3.     "bufio"
  4.     "fmt"
  5.     "os"
  6. )
  7. func tryDefer() {
  8.     defer fmt.Println(2)
  9.     defer fmt.Println(1)
  10.     fmt.Println(3)
  11.     fmt.Println(4)
  12. }
  13. func writeFile(filename string) {
  14.     file, err := os.Create(filename)
  15.     if err != nil {
  16.         panic(err)
  17.     }
  18.     defer file.Close()
  19.     writer := bufio.NewWriter(file)
  20.     defer writer.Flush()
  21.     for i := 0; i < 20; i++ {
  22.         fmt.Fprintln(writer, i)
  23.     }
  24. }
  25. func writeFile2(filename string) {
  26.     file, err := os.OpenFile(
  27.         filename, os.O_EXCL|os.O_CREATE, 0666)
  28.     if err != nil {
  29.         panic(err)
  30.     }
  31.     defer file.Close()
  32.     writer := bufio.NewWriter(file)
  33.     defer writer.Flush()
  34.     for i := 0; i < 20; i++ {
  35.         fmt.Fprintln(writer, i)
  36.     }
  37. }
  38. func main() {
  39.     writeFile2("fib.txt")
  40.     /**
  41.     panic: open fib.txt: The file exists.
  42.     goroutine 1 [running]:
  43.     main.writeFile2({0xf7b58, 0xc000040000})
  44.         E:/Projects/GolandProjects/go-camp/mooc/code/learngo/errhandling/defer/defer.go:35 +0x1d5
  45.     main.main()
  46.         E:/Projects/GolandProjects/go-camp/mooc/code/learngo/errhandling/defer/defer.go:47 +0x25
  47.     Process finished with the exit code 2
  48.      */
  49. }

如果文件存在就报错

可以处理一下

  1. func writeFile2(filename string) {
  2.     file, err := os.OpenFile(
  3.         filename, os.O_EXCL|os.O_CREATE, 0666)
  4.     if err != nil {
  5.         fmt.Println("flie already exist!!!")
  6.         return
  7.     }
  8.     defer file.Close()
  9.     writer := bufio.NewWriter(file)
  10.     defer writer.Flush()
  11.     for i := 0; i < 20; i++ {
  12.         fmt.Fprintln(writer, i)
  13.     }
  14. }

真正的处理错误

  1. func writeFile2(filename string) {
  2.     file, err := os.OpenFile(
  3.         filename, os.O_EXCL|os.O_CREATE, 0666)
  4.     if err != nil {
  5.         if pathError, ok := err.(*os.PathError); !ok {
  6.             // 真的 不知道是森什么错了
  7.             // 那就挂掉程序吧
  8.             panic(err)
  9.         } else {
  10.             fmt.Printf("%s, %s, %s\n",
  11.                 pathError.Op,
  12.                 pathError.Path,
  13.                 pathError.Err,
  14.             )
  15.         }
  16.         return
  17.     }
  18.     defer file.Close()
  19.     writer := bufio.NewWriter(file)
  20.     defer writer.Flush()
  21.     for i := 0; i < 20; i++ {
  22.         fmt.Fprintln(writer, i)
  23.     }
  24. }

3-3 服务器统一出错处理浏览器需放大.mp4

3-4 服务器统一出错处理.mp4

error vs panic

  • 意料之中: 使用error . 如文件打不开
  • 意料之外: 使用panic . 如数组越界

第3章_错误处理和资源管理 - 图2
输入的参数类型是函数
输出的返回类型也是函数