pointers - 戈朗 : interface func to print memory address

Question

我很好奇为什么直接在 var 上打印内存地址有效，但尝试通过接口(interface)执行相同的操作却无法打印出内存地址？

package main

import "fmt"

type address struct {
    a int
}

type this interface {
    memory()
}

func (ad address) memory() {
    fmt.Println("a - ", ad)
    fmt.Println("a's memory address --> ", &ad)
}

func main() {
    ad := 43
    fmt.Println("a - ", ad)
    fmt.Println("a's memory address --> ", &ad)

    //code init in here
    thisAddress := address{
        a: 42,
    }
    // not sure why this doesnt return memory address as well?
    var i this
    i = thisAddress
    i.memory()
}

https://play.golang.org/p/Ko8sEVfehv

只是想在修复错误后添加它，它现在可以按预期运行。测试移位内存指针

package main

import "fmt"

type address struct {
  a int
}

type this interface {
  memory() *int
}

func (ad address) memory() *int {

  /*reflect.ValueOf(&ad).Pointer() research laws of reflection */
  var b = &ad.a

  return b
}

func main() {



  thisAddress := address{
      a: 42,
  }
  thatAddress := address{
      a: 43,
  }

  var i this
  i = thisAddress
  a := i.memory()

  fmt.Println("I am retruned", a)
  fmt.Println("I am retruned", *a)
  i = thatAddress
  c := i.memory()
  fmt.Println("I am retruned", c)
  fmt.Println("I am retruned", *c)
}

https://play.golang.org/p/BnB14-yX8B

Answer 1

因为在 memory() 方法中的第二种情况:

func (ad address) memory() {
    fmt.Println("a - ", ad)
    fmt.Println("a's memory address --> ", &ad)
}

ad 不是int 而是一个结构，ad 是address 类型。您打印的不是 int 的地址，而是 struct 的地址。指向结构的指针的默认格式为:&{}。

引用自 fmt 的包文档关于默认格式:

struct:             {field0 field1 ...}
array, slice:       [elem0 elem1 ...]
maps:               map[key1:value1 key2:value2]
pointer to above:   &{}, &[], &map[]

如果您修改该行以打印类型为 int 的 address.a 字段的地址:

fmt.Println("a's memory address --> ", &ad.a)

您将看到以十六进制格式打印的相同指针格式，例如:

a's memory address -->  0x1040e13c