如何打印整个url.URL结构？

Question

I have the following https://play.golang.org/p/utnlHJqlX1:

package main

import (
    "fmt"
    "net/url"
)

func main() {
    u, err := url.Parse("http://www.something.com")
    if err != nil {
        fmt.Println(err)
    }

    fmt.Printf("%+v", u)
}

I was expecting the "%+v" to print the struct and the fields. Instead it prints: "http://www.something.com"

Answer 1

It seems to be because Parse is returning a pointer to the struct.

Try with this (note the *):

fmt.Printf("%+v
", *u)

Modified playground:

https://play.golang.org/p/Grjrp2QriK

EDIT

To expand on this, the reason for this is that fmt treats structs that implement Stringer differently when doing %+v.

This is the relevant code: https://golang.org/src/fmt/print.go?s=4772:4849#L577

Since *URL implements Stringer: https://golang.org/pkg/net/url/#URL.String

That's the string being used.

By dereferencing the pointer, we get an URL, which does not implement the interface (cause the receiver in the String method is a pointer).