函数中输入参数的变量类型

huangapple
go评论111阅读模式
英文:

Variable type of input parameter in function

问题

我创建了一个函数，用于获取用户在Pull Request上的最后一条评论。我正在使用"github.com/google/go-github/github"包。我想要将其用于[]*github.IssueComment和[]*github.PullRequestComment类型。有没有一种方法可以使输入参数的类型是可变的，这样我就不需要在函数定义中指定它，函数可以使用任一类型进行调用？

  1. func getLastUserInteractionPR(comments_array *github.IssueComment OR *github.PullRequestComment)(*github.IssueComment OR *github.PullRequestComment) {
  2. }

使用泛型的方式：

  1. func getLastUserInteractionPR(comments_array any)(any) {
  2. }

这是一种紧急解决方案，因为我正在使用Go 1.14编写整个项目，而这个功能在Go 1.18中才可用。

当我尝试使用空接口{}作为输入类型时：

  1. func getLastUserInteractionPRIssue(comments_array interface{})(*github.IssueComment) {
  3. comments_array []*github.IssueComment(comments_array); err {
  4. fmt.Println("success")
  5. 	} else {
  6. 		fmt.Println("failure")
  7. 	}
  8. }
英文:

I created a function that gets the last comment of a user on Pull Request. I am using "github.com/google/go-github/github" package. I would like to use it for []*github.IssueComment and []*github.PullRequestComment type. Is there a way for the type of the input parameter to be variable so I dont have to specify it in the function definition and function can be called using either of the type?

  1. func getLastUserInteractionPR(comments_array *github.IssueComment OR *github.PullRequestComment)(*github.IssueComment OR *github.PullRequestComment) {
  2. }

Using of generics:

  1. func getLastUserInteractionPR(comments_array any)(any) {
  2. }

is a emergency solution, since the whole project I am working on is written in Go 1.14 and this funcionality is available from GO 1.18

When I try to use empty interface{} as input type:

  1. func getLastUserInteractionPRIssue(comments_array interface{})(*github.IssueComment) {
  3. comments_array []*github.IssueComment(comments_array); err {
  4. fmt.Println("success")
  5. 	} else {
  6. 		fmt.Println("failure")
  7. 	}
  8. }
  11. </details>
  14. # 答案1
  15. **得分**: 1
  17. 你关心例如`IssueComment`的内部结构吗？
  18. ```go
  19. type IssueComment struct {
  20. 	ID        *int64     `json:"id,omitempty"`
  21. 	NodeID    *string    `json:"node_id,omitempty"`
  22. 	Body      *string    `json:"body,omitempty"`
  23. 	User      *User      `json:"user,omitempty"`
  24. 	Reactions *Reactions `json:"reactions,omitempty"`
  25. 	CreatedAt *time.Time `json:"created_at,omitempty"`
  26. 	UpdatedAt *time.Time `json:"updated_at,omitempty"`
  27. 	// AuthorAssociation是评论作者与问题存储库的关系。
  28. 	// 可能的值有"COLLABORATOR"、"CONTRIBUTOR"、"FIRST_TIMER"、"FIRST_TIME_CONTRIBUTOR"、"MEMBER"、"OWNER"或"NONE"。
  29. 	AuthorAssociation *string `json:"author_association,omitempty"`
  30. 	URL               *string `json:"url,omitempty"`
  31. 	HTMLURL           *string `json:"html_url,omitempty"`
  32. 	IssueURL          *string `json:"issue_url,omitempty"`
  33. }

也就是说，你关心从中提取一些特定字段吗？PullRequestComment是一个更大的结构体（它有更多的字段），你关心从中提取一些字段吗？

还是你只想要每个结构体的字符串表示？你要做的事情很大程度上取决于你想要对传递的值做什么。

如果你只想要每个结构体的string表示，你可以使用极端的（而且，老实说，不太安全 - 我不推荐这样做）示例，让你的函数接受一个fmt.Stringer对象的切片：

  1. func DoStuffWithStringifiedComments(cs []fmt.Stringer) {
  2.   // IssueComment和PullRequestComment都提供了String()方法，因此实现了fmt.Stringer
  3.   for _, comment := range cs {
  4.     DoSomethingWith(comment.String())
  5.   }
  6. }

现在你的切片可以包含任何类型的对象，而不会出错。缺点是：它也可以包含其他你不想要的类型。所以你需要添加一个类型断言检查：

  1. switch t := comment.(type) {
  2.   case github.IssueComment:
  3.     // 做一些好的事情
  4.   case github.PullRequestComment:
  5.     // 做其他好的事情
  6.   default:
  7.     // 对t的值进行报错和警告
  8. }

如果有你想要提取的字段，你需要结合一个接受类似[]interface{}的函数（将其作为空接口的切片，而不是作为空接口代替切片），迭代它并对切片的每个元素进行类型检查，只要元素是你期望的类型，就提取出有意义的字段：

  1. func DoStuff(comments []interface{}) error {
  2.   for _, c := range comments {
  3.     if ic, ok := c.(*github.IssueComment); ok { // 如果你的切片包含的是值而不是引用，请删除解引用
  4.       // 提取字段并执行IssueComment特定的操作
  5.       ProcessIssueComment(ic)
  6.     } else if prc, ok := c.(*github.PullRequestComment); ok {
  7.       // 执行PRComment特定的操作
  8.       ProcessPullRequestComment(prc)
  9.     } else {
  10.       return fmt.Errorf("我不想要类型为%s的东西", t)
  11.     }
  12.   }
  13.   return nil
  14. }

另外：游说项目所有者（如果不是你）升级到当前版本的Go。1.14只在2020年发布，但在Go发布中已经是一个漫长的时间了。

英文:

Do you care about the internal structure of e.g. an IssueComment?

  1. type IssueComment struct {
  2. 	ID        *int64     `json:&quot;id,omitempty&quot;`
  3. 	NodeID    *string    `json:&quot;node_id,omitempty&quot;`
  4. 	Body      *string    `json:&quot;body,omitempty&quot;`
  5. 	User      *User      `json:&quot;user,omitempty&quot;`
  6. 	Reactions *Reactions `json:&quot;reactions,omitempty&quot;`
  7. 	CreatedAt *time.Time `json:&quot;created_at,omitempty&quot;`
  8. 	UpdatedAt *time.Time `json:&quot;updated_at,omitempty&quot;`
  9. 	// AuthorAssociation is the comment author&#39;s relationship to the issue&#39;s repository.
  10. 	// Possible values are &quot;COLLABORATOR&quot;, &quot;CONTRIBUTOR&quot;, &quot;FIRST_TIMER&quot;, &quot;FIRST_TIME_CONTRIBUTOR&quot;, &quot;MEMBER&quot;, &quot;OWNER&quot;, or &quot;NONE&quot;.
  11. 	AuthorAssociation *string `json:&quot;author_association,omitempty&quot;`
  12. 	URL               *string `json:&quot;url,omitempty&quot;`
  13. 	HTMLURL           *string `json:&quot;html_url,omitempty&quot;`
  14. 	IssueURL          *string `json:&quot;issue_url,omitempty&quot;`
  15. }

As in, do you care about extracting some specific field from that? PullRequestComment is a larger struct (it has more fields), do you care about extracting some field from that?

Or do you just want a string representation of each? What you do very much depends on what you want to do with the passed value(s).

If you just want a string representation of each, you could use the extreme (and, honestly, not very safe - I don't recommend this) example of having your function accept a slice of fmt.Stringer objects:

  1. func DoStuffWithStringifiedComments(cs []fmt.Stringer) {
  2.   // Both IssueComment and PullRequestComment provide String()
  3.   // methods and therefore implement fmt.Stringer
  4.   for _, comment := range cs {
  5.     DoSomethingWith(comment.String())
  6.   }
  7. }

Your slice can now include objects of either type and nothing will blow up. Downside: it can also include a couple of bajillion other types, none of which you want. So you'd need to add a type assertion check:

  1. switch t := comment.(type) {
  2.   case github.IssueComment:
  3.     // Do good stuff
  4.   case github.PullRequestComment:
  5.     // Do other good stuff
  6.   default:
  7.     // Yell and scream about the value of t
  8. }

If there are fields you want to extract, you're going to have to combine a function taking something like []interface{} (make it a slice of empty interfaces, not an empty interface standing in for the slice), iterate over it and do a type check on each element of the slice, and pull out whatever fields are meaningful as long as the element is of a type you expect:

  1. func DoStuff(comments []interface{}) error {
  2.   for _, c : = range comments {
  3.     if ic, ok := c.(*github.IssueComment); ok { // Remove the deref if your slice contains values, not references
  4.       // Pull out fields and do IssueComment-specific things
  5.       ProcessIssueComment(ic)
  6.     } else if prc, ok := c.(*github.PullRequestComment); ok {
  7.       // Do PRComment-specific things
  8.       ProcessPullRequestComment(prc)
  9.     } else {
  10.       return(fmt.Errorf(&quot;I did not want something of type %s&quot;, t))
  11.     }
  12.   }
  13.   return nil
  14. }

Also: lobby the project owner (if that isn't you) to move to a current version of go. 1.14 only came out in 2020, but that's an eternity in go releases.

huangapple
  • 本文由 发表于 2023年1月17日 00:27:37
  • 转载请务必保留本文链接：https://go.coder-hub.com/75137033.html
  • go
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