golang-反射包中的Elem Vs Indirect [英] golang - Elem Vs Indirect in the reflect package

问题描述

来自文档

  func(v值)Elem()值 

Elem返回接口v包含的值或指针v指向的值.如果v的Kind不是Interface或Ptr，则会感到恐慌.如果v为零，则返回零值.

  func间接(v值)值 

Indirect返回v指向的值.如果v是nil指针，则Indirect返回零值.如果v不是指针，则Indirect返回v.

那么我可以安全地假设以下内容吗?

  reflect.Indirect(reflect.ValueOf(someX))=== reflect.ValueOf(someX).Elem(). 

间接方法只是上面右侧的一种便捷方法吗?

解决方案

如果 reflect.Value 是指针，则 v.Elem()等效于 reflect.Indirect(v).如果不是指针，则它们不是等效的:

• 如果该值是接口，则 reflect.Indirect(v)将返回相同的值，而 v.Elem()将返回所包含的动态值./li>
• 如果该值是其他值，则 v.Elem()会惊慌.

reflect.Indirect 帮助程序用于需要接受特定类型或指向该类型的指针的情况.一个示例是 database/sql 转换例程:通过使用 reflect.Indirect ，它可以使用相同的代码路径来处理各种类型和指向这些类型的指针.

From the docs

func (v Value) Elem() Value

Elem returns the value that the interface v contains or that the pointer v points to. It panics if v's Kind is not Interface or Ptr. It returns the zero Value if v is nil.

func Indirect(v Value) Value

Indirect returns the value that v points to. If v is a nil pointer, Indirect returns a zero Value. If v is not a pointer, Indirect returns v.

So can I safely assume the following?

reflect.Indirect(reflect.ValueOf(someX)) === reflect.ValueOf(someX).Elem().

Is Indirect method just a convenience method for the right hand side of the above?

解决方案

If a reflect.Value is a pointer, then v.Elem() is equivalent to reflect.Indirect(v). If it is not a pointer, then they are not equivalent:

• If the value is an interface then reflect.Indirect(v) will return the same value, while v.Elem() will return the contained dynamic value.
• If the value is something else, then v.Elem() will panic.

The reflect.Indirect helper is intended for cases where you want to accept either a particular type, or a pointer to that type. One example is the database/sql conversion routines: by using reflect.Indirect, it can use the same code paths to handle the various types and pointers to those types.

这篇关于golang-反射包中的Elem Vs Indirect的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！