英文:
Get fields of empty struct slice in Go
问题
我有一个函数：
func (r *render) foo(v interface{}) {val := reflect.ValueOf(v)fields := structs.Fields(val.Index(0).Interface())...}
该函数接受一个结构体切片，并尝试获取v的字段，但是如果v为空，则"val.Index(0)"会导致程序崩溃。有没有更好的方法来解决这个问题？
英文:
I have a function
func (r *render) foo(v interface{}) {val := reflect.ValueOf(v)fields := structs.Fields(val.Index(0).Interface())...
Which takes a slice of structs and tries to get the fields of v,
however if v is empty then "val.Index(0)" crashes the program. Is there a better way to do this?
答案1
得分: 2
你需要首先检查是否有一个切片，然后检查是否有一个空切片，同时你可能也应该检查是否有一个结构体：（示例）
val := reflect.ValueOf(v)if val.Kind() != reflect.Slice {fmt.Println("不是一个切片")return}if val.Len() == 0 {fmt.Println("空切片")return}if val.Index(0).Kind() != reflect.Struct {fmt.Println("不是一个结构体切片")return}fields := structs.Fields(val.Index(0).Interface())...
如果你只想从结构体类型中获取字段，而不管切片是否为空，你可以使用切片类型的Elem方法来提取它（示例）
// 获取切片的内部类型t := val.Type().Elem()if t.Kind() != reflect.Struct {fmt.Println("不是一个结构体")return}fmt.Println("类型:", t)for i := 0; i < t.NumField(); i++ {fmt.Println(t.Field(i).Name)}
英文:
You need to check first if you have a slice to begin with, then check if you have an empty slice, and you probably should check that you have a struct too while you're at it: (example)
val := reflect.ValueOf(v)if val.Kind() != reflect.Slice {fmt.Println("not a slice")return}if val.Len() == 0 {fmt.Println("empty slice")return}if val.Index(0).Kind() != reflect.Struct {fmt.Println("not a slice of structs")return}fields := structs.Fields(val.Index(0).Interface())...
If you only want the fields from a struct type, regardless of if the slice is empty, you can use the slice type's Elem method to extract it (example)
// get the internal type of the slicet := val.Type().Elem()if t.Kind() != reflect.Struct {fmt.Println("not a struct")return}fmt.Println("Type:", t)for i := 0; i < t.NumField(); i++ {fmt.Println(t.Field(i).Name)}
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