douci1677
2017-09-17 15:37 阅读 19
已采纳

通过fmt.Scan设置结构的值

I want to synchronize state between map[string]string and custom Go structure and came to a conclusion that simplest way to parse it is to use fmt.Sscan for fields.

Unfortunately, direct approach is not working (playground):

var S struct{ I int }

f := reflect.Indirect(reflect.ValueOf(&S)).Field(0)
fmt.Sscan("10", f.Interface())
fmt.Println(S) // {0}

Introducing an intermediate value and using Set(), however, solves the issue:

nv := reflect.New(f.Type())
fmt.Sscan("10", nv.Interface())
f.Set(reflect.Indirect(nv))
fmt.Println(S) // {10}

I wonder why the first approach didn't work. Isn't Interface() returns a kind of reference to a field which can be used to change its value?

  • 点赞
  • 写回答
  • 关注问题
  • 收藏
  • 复制链接分享

1条回答 默认 最新

  • 已采纳
    dongqiao8502 dongqiao8502 2017-09-17 16:25

    The Interface() method returns the value, not a reference to the value. Take the address (by calling Addr()) of the field to scan directly to the field:

    var S struct{ I int }
    f := reflect.Indirect(reflect.ValueOf(&S)).Field(0)
    fmt.Sscan("10", f.Addr().Interface())  
    fmt.Println(S) // {0}
    

    https://play.golang.org/p/6_4DjiFZB2

    点赞 评论 复制链接分享

相关推荐