Golang switch between structs

huangapple
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英文:

Golang switch between structs

问题

我是你的中文翻译助手，以下是你要翻译的内容：

我刚开始学习golang，我正在尝试创建一个函数，根据它所用的结构体，将返回一个使用Sprintf格式化的字符串。

  1. type Name struct {
  2.     Title string
  3.     First string
  4.     Last  string
  5. }
  7. type Location struct {
  8.     Street string
  9.     City   string
  10.     State  string
  11.     Zip    string
  12. }
  14. func Merge(m interface{}) string {
  15.     switch m.(type) {
  16.     case *Location:
  17.         return fmt.Sprintf("%s \n %s, %s %s", m.(*Location).Street, m.(*Location).City, m.(*Location).State, m.(*Location).Zip)
  18.     case *Name:
  19.         return fmt.Sprintf("%s. %s %s", m.(*Name).Title, m.(*Name).First, m.(*Name).Last)
  20.     }
  21.     return "Not Applicable"
  22. }
  24. fmt.Println(Merge(Location))

我从我的PrintLn中得到了" Not Applicable"的消息。在代码的一个版本中，我相信这个消息是" out of index"。

英文:

I'm new to golang and I'm trying to create a function that, based on the struct it's used on, will return a formatted string using Sprintf

  1. type Name struct {
  2.     Title string
  3.     First string
  4.     Last  string
  5. }
  7. type Location struct {
  8.     Street string
  9.     City   string
  10.     State  string
  11.     Zip    string
  12. }
  14. func Merge(m interface{}) string {
  15.     switch m.(type) {
  16.     case *Location:
  17. 	    return fmt.Sprintf("%s \n %s, %s %s", m.(*Location).Street, m.(*Location).City, m.(*Location).State, m.(*Location).Zip)
  18.     case *Name:
  19. 	    return fmt.Sprintf("%s. %s %s", m.(*Name).Title, m.(*Name).First, m.(*Name).Last)
  20.     }
  21.     return "Not Applicable"
  22. }
  24. fmt.Println(Merge(Location))

I'm getting the "Not Applicable" message from my PrintLn. In one version of the code, I believe the message was "out of index".

答案1

得分: 9

在你的示例中，你试图将结构体本身传递给函数，而不是结构体的实例。当我运行你的代码时，它无法编译。不过，我同意上面的评论，通过确保每个结构体满足fmt.Stringer接口来处理会更好。

fmt.Stringer接口

修复后的代码：

  1. package main
  3. import "fmt"
  5. type Name struct {
  6.     Title string
  7.     First string
  8.     Last  string
  9. }
  11. type Location struct {
  12.     Street string
  13.     City   string
  14.     State  string
  15.     Zip    string
  16. }
  18. func Merge(m interface{}) string {
  19.     switch m.(type) {
  20.     case Location:
  21.         return fmt.Sprintf("%s \n %s, %s %s", m.(Location).Street, m.(Location).City, m.(Location).State, m.(Location).Zip)
  22.     case Name:
  23.         return fmt.Sprintf("%s. %s %s", m.(Name).Title, m.(Name).First, m.(Name).Last)
  24.     }
  25.     return "Not Applicable"
  26. }
  28. func main() {
  29.     l := Location{
  30.         Street: "122 Broadway",
  31.         City:   "New York",
  32.         State:  "NY",
  33.         Zip:    "1000",
  34.     }
  35.     fmt.Println(Merge(l))
  36. }

使用fmt.String的版本：

  1. package main
  3. import "fmt"
  5. type Name struct {
  6.     Title string
  7.     First string
  8.     Last  string
  9. }
  11. func (n *Name) String() string {
  12.     return fmt.Sprintf("%s. %s %s", n.Title, n.First, n.Last)
  13. }
  15. type Location struct {
  16.     Street string
  17.     City   string
  18.     State  string
  19.     Zip    string
  20. }
  22. func (l *Location) String() string {
  23.     return fmt.Sprintf("%s \n %s, %s %s", l.Street, l.City, l.State, l.Zip)
  24. }
  26. func main() {
  27.     l := &Location{
  28. 	    Street: "120 Broadway",
  29. 	    City:   "New York",
  30. 	    State:  "NY",
  31. 	    Zip:    "1000",
  32.     }
  33.     fmt.Println(l)
  35.     n := &Name{
  36. 	    Title: "Mr",
  37. 	    First: "Billy",
  38. 	    Last:  "Bob",
  39.     }
  40.     fmt.Println(n)
  41. }
英文:

In your example you are trying to pass the struct itself to the function rather than an instance of the struct. When I ran your code it wouldn't compile. I agree with the comments above though, this would be much better handled by making sure each struct satisfies the fmt.Stringer interface.

fmt.Stringer interface

A fixed version of your code:

  1. package main
  3. import "fmt"
  5. type Name struct {
  6.     Title string
  7.     First string
  8.     Last  string
  9. }
  11. type Location struct {
  12.     Street string
  13.     City   string
  14.     State  string
  15.     Zip    string
  16. }
  18. func Merge(m interface{}) string {
  19.     switch m.(type) {
  20.     case Location:
  21.         return fmt.Sprintf("%s \n %s, %s %s", m.(Location).Street, m.(Location).City, m.(Location).State, m.(Location).Zip)
  22.     case Name:
  23.         return fmt.Sprintf("%s. %s %s", m.(Name).Title, m.(Name).First, m.(Name).Last)
  24.     }
  25.     return "Not Applicable"
  26. }
  28. func main() {
  29.     l := Location{
  30.         Street: "122 Broadway",
  31.         City: "New York",
  32.         State: "NY",
  33.         Zip: "1000",
  34.     }
  35.     fmt.Println(Merge(l))
  36. }

A version using fmt.String:

  1. package main
  3. import "fmt"
  5. type Name struct {
  6.     Title string
  7.     First string
  8.     Last  string
  9. }
  11. func (n *Name) String() string {
  12.     return fmt.Sprintf("%s. %s %s", n.Title, n.First, n.Last)
  13. }
  15. type Location struct {
  16.     Street string
  17.     City   string
  18.     State  string
  19.     Zip    string
  20. }
  22. func (l *Location) String() string {
  23.     return fmt.Sprintf("%s \n %s, %s %s", l.Street, l.City, l.State, l.Zip)
  24. }
  26. func main() {
  27.     l := &Location{
  28. 	    Street: "120 Broadway",
  29. 	    City:   "New York",
  30. 	    State:  "NY",
  31. 	    Zip:    "1000",
  32.     }
  33.     fmt.Println(l)
  35.     n := &Name{
  36. 	    Title: "Mr",
  37. 	    First: "Billy",
  38. 	    Last:  "Bob",
  39.     }
  40.     fmt.Println(n)
  41. }

huangapple
  • 本文由 发表于 2015年6月16日 09:59:52
  • 转载请务必保留本文链接：https://go.coder-hub.com/30857687.html
  • go
  • interface
  • struct
  • switch-statement
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