如何在Golang中检查指向结构net.IPNet的Pointer的nil值

Question

How can I check the nil value as a result of the assignment of variable b below?

package main

import (
    "fmt"
    "net"
)


type Subnet struct {
    ID                int
    IP                *net.IPNet
}

func main() {
    var s = Subnet{
        ID: 12345,
        IP: &net.IPNet{
            IP:   net.IP{10, 1, 232, 0},
            Mask: net.IPMask{255, 255, 255, 0},
        },
    }
    fmt.Printf("%+v
", s)
    var b = Subnet{
        ID: 12345,
        IP: &net.IPNet{},
    }
    fmt.Printf("%+v
", b)
    if b.IP == nil {
        fmt.Println("hello there")
    }
}

Here is the go playground https://play.golang.org/p/Jk6_3ofyH5

Basically, I expect that "hello there" will be printed out as b.IP is nil, but it did not.

Answer 1

The check should be like, if b.IP != nil { fmt.Println("hello there") } And the output will have hello-world,

{ID:12345 IP:10.1.232.0/24} {ID:12345 IP:} hello there

Note:Golang's nil is not same as Cpp's NULL, it is the opposite.