go - 为什么在地址上取消引用会在 golang 中产生 "invalid indirect"错误？

Question

type person struct{
  Name string
  Age int
}

// parameters : (pointer to person struct), which is basically address of person object
func printPerson(p *person) {

  // when we add '*' to a address, then it becomes dereferencing, Hence 
  // I read "*p.Name" as "person object dot Name" and i expect it to give value,
  // I get this error:
  // ./prog.go:20:15: invalid indirect of p.Name (type string)
  // ./prog.go:20:24: invalid indirect of p.Age (type int)
  fmt.Println(*p.Name, *p.Age) // does not works, ERROR THROWN

  // But this works perfectly
  // I read it as "person address dot name and person address dot age"
  // for me it does not make sense when we say "address dot field name", 
  // shouldn't it be "object dot field name ? "
  fmt.Println(p.Name, p.Age)
}
func main() {
  p := person{"foobar", 23}
  printPerson(&p) // we are sending address to the method
}

为什么我们不能执行取消引用的对象点字段名而不是地址点字段名？请阅读代码注释以获取问题解释，我在这里缺少什么？

Answer 1

p.Name 和 p.Age 按原样工作，因为如果 p 是指向结构的指针，那么 p.Name 是 (*p).Name 的简写。引自 Spec: Selectors:

In the expression x.f [...] if the type of x is a defined pointer type and (*x).f is a valid selector expression denoting a field (but not a method), x.f is shorthand for (*x).f.

鉴于此，*p.Name 不会尝试取消引用 p 并引用 Name 字段，它会尝试取消引用不是指针的 p.Name 字段。

如果您使用括号来对间接寻址进行分组，它会起作用:

fmt.Println((*p).Name, (*p).Age)

但同样，由于这种形式非常常见，规范允许您省略指针间接寻址并简单地编写 p.Name。