英文:
Why the & operator on struct doesn't return a digital address?
问题
我刚开始学习 Golang。
我发现 & 运算符在简单类型和结构体中的行为不同。
-
对于简单类型，
&返回一个地址。 -
对于结构体，它返回其他内容。
代码：
package main
import "fmt"
type person struct {
name string
age int
}
func main() {
s1 := "abc"
fmt.Println("s1 address =", &s1)
s2 := person{"Sam", 55}
fmt.Println("s2 address =", &s2)
}
输出：
[ `hello` | done: 79.0079ms ]
s1 address = 0xc04203c1e0
s2 address = &{Sam 55} <======== 这是什么？为什么不是像上面那样的地址？
再次强调，这个设计是“必须的”还是“偶然的”？
英文:
I just started to learn the golang.
I found the & operator behaves differently for simple type and struct.
-
For simple type,
&returns an address. -
For struct, it returns something else.
Code:
package main
import "fmt"
type person struct {
name string
age int
}
func main() {
s1 := "abc"
fmt.Println("s1 address =", &s1)
s2 := person{"Sam", 55}
fmt.Println("s2 address = ", &s2)
}
Output:
[ `hello` | done: 79.0079ms ]
s1 address = 0xc04203c1e0
s2 address = &{Sam 55} <======== What's this? And why not some address like above?
Again, is this design a have-to or a happen-to?
答案1
得分: 10
& 单元操作符在内置类型和结构体中的行为相同，它用于获取变量的内存地址。在这个例子中，我们会看到 &{Sam 55}，因为Go语言默认会检查 fmt.Println() 中的参数是结构体还是指向结构体的指针，并在这种情况下尝试打印结构体的每个字段以进行调试。但是，如果你想要看到一个指针，你可以使用 fmt.Printf() 和 %p，像这样：
func main() {
s1 := "abc"
fmt.Println("s1 address =", &s1)
s2 := person{"Sam", 55}
fmt.Println("s2 as pointer =", &s2)
fmt.Printf("s2 address = %p value with fields %+v", &s2, s2)
}
额外提示：你可以使用 %+v 来打印字段名和值。
链接：https://play.golang.org/p/p7OVRu8YWB
英文:
The unitary operator & behaves the same for builtin types and structs, it's used to get the memory address of a var. In this case we'll see &{Sam 55} because Go always checks by default if the parameter in fmt.Println() is a struct or a pointer to struct and in that case will try to print each field of the struct for debugging purposes, but if you want to see a pointer you can use fmt.Printf() with %p, like this:
func main() {
s1 := "abc"
fmt.Println("s1 address =", &s1)
s2 := person{"Sam", 55}
fmt.Println("s2 as pointer =", &s2)
fmt.Printf("s2 address = %p value with fields %+v", &s2, s2)
}
Bonus: you can use %+v to print field names and values
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