Golang edit array of struts from main() to function

huangapple
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英文:

Golang edit array of struts from main() to function

问题

希望你能帮忙，以下是我代码的简化版本。

基本上，我将一个结构体数组传递给floatInSlice()函数，其中要么向数组中添加一个新的结构体，要么将现有结构体的AudienceCategory.Sum增加1。

总体上都工作得很好，除了b.Sum = b.Sum+1这一行。

现在我知道，如果我想将一个对象作为指针而不是值传递，我需要使用*和&，但是我似乎无法让它工作，非常感谢任何帮助！

  1. type AudienceCategory struct {
  2.     Cat int
  3.     Sum int
  4. }
  6. var counter = []AudienceCategory{}
  8. func main() {
  9.     for i := 1; i < len(words); i++ {
  10.         counter = floatInSlice(category, counter)
  11.         if counter != nil {}
  12.     }
  13.     fmt.Printf("%v ", counter)
  14. }
  16. func floatInSlice(category int, counter *[]AudienceCategory) []AudienceCategory {
  17.     for _, b := range counter {
  18.         if b.Cat == category {
  19.             b.Sum = b.Sum+1
  20.             return counter
  21.         }
  22.     }
  23.     x := AudienceCategory{Cat: category, Sum: 1}
  24.     counter = append(counter, x)
  25.     return counter
  26. }

编辑***********

最后终于搞定了，感谢大家的帮助！

  1. func floatInSlice(category int, counter []AudienceCategory) []AudienceCategory {
  2.     for i := 0; i < len(counter); i++ {
  3.         if counter[i].Cat == category {
  4.             counter[i].Sum = counter[i].Sum+1
  5.             return counter
  6.         }
  7.     }
  8.     x := AudienceCategory{Cat: category, Sum: 1}
  9.     counter = append(counter, x)
  10.     return counter
  11. }
英文:

hoping you can help below is a concise version of my code.

basically im passing an array of structs to floatInSlice() in which either a new struct gets added to the array or an existing struct AudienceCategory.Sum gets ++

all is generally working fine except for the b.Sum = b.Sum+1

Now I know that if I want to pass an obect as a pointer rather than value I need to use */& but I just cant seem to get it working, any help much appriciated!

  1. type AudienceCategory struct {
  2.     Cat int
  3.     Sum int
  4. }
  7. var counter = []AudienceCategory{}
  10. func main() {
  11.      for i := 1; i &lt; len(words); i++ {
  12.          counter = floatInSlice(category,counter)
  13. 		if counter != nil{}
  14.      }
  15.      fmt.Printf(&quot;%v &quot;, counter) 
  16. }
  19. func floatInSlice(category int, counter *[]AudienceCategory) []AudienceCategory {
  20.     for _, b := range counter {
  21.         if b.Cat == category {
  22.     	    b.Sum = b.Sum+1
  23.     	
  24.     	    return counter
  25.         }
  26.     }
  27.     x := AudienceCategory{Cat:category,Sum:1}
  28.     counter = append( counter, x)
  29.     return counter
  30. }

EDIT ***********

got it working in the end thanks for the help guys

  1. func floatInSlice(category int, counter []AudienceCategory) []AudienceCategory {
  2. 	
  3.     for i := 0; i &lt; len(counter); i++ {
  4. 	    if counter[i].Cat == category {
  5.             counter[i].Sum = counter[i].Sum+1
  7.             return counter
  8.         }
  9.     }
  10.     x := AudienceCategory{Cat:category,Sum:1}
  11.     counter = append( counter, x)
  12.     return counter
  13. }

答案1

得分: 1

当你在_, b := range counter中使用值范围时，b包含counter的每个元素的副本。所以你正在对一个丢失的副本求和，而不是对切片中的元素求和。

你应该使用以下代码：

  1. func floatInSlice(category int, counter *[]AudienceCategory) []AudienceCategory {
  2.     for i, b := range *counter {
  3.         if b.Cat == category {
  4.             (*counter)[i].Sum = (*counter)[i].Sum+1
  6.             return counter
  7.         }
  8.     }
  9.     x := AudienceCategory{Cat:category,Sum:1}
  10.     counter = append( counter, x)
  11.     return counter
  12. }

这样你就可以正确地对切片中的元素进行求和了。

英文:

When you use value range as in _, b := range counter, b contains a copy of each element of counter. So you are summing a copy that is lost, not the element in the slice.

You should use

  1. func floatInSlice(category int, counter *[]AudienceCategory) []AudienceCategory {
  2.     for i, b := range *counter {
  3.         if b.Cat == category {
  4.             (*counter)[i].Sum = (*counter)[i].Sum+1
  6.             return counter
  7.         }
  8.     }
  9.     x := AudienceCategory{Cat:category,Sum:1}
  10.     counter = append( counter, x)
  11.     return counter
  12. }

huangapple
  • 本文由 发表于 2014年9月12日 02:38:44
  • 转载请务必保留本文链接：https://go.coder-hub.com/25794780.html
  • go
  • pointers
  • struct
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