为什么我不能使用flag.StringVar传递指向fmt.Println的指针？

Question

I've started looking at Golang, and following an example to pass in command line arguments, I've got this code:

package main

import (
    "flag"
    "fmt"
)

func main() {

    wordPtr := flag.String("namestring", "stringvalue", "Pass in a string")
    numPtr := flag.Int("number", 11, "Pass in an int")
    boolPtr := flag.Bool("switchflag", false, "Pass in a bool")
    var svar string
    flag.StringVar(&svar, "svar", "svarstringvalue", "A string variable")
    flag.Parse()

    fmt.Println("Word:", *wordPtr)
    fmt.Println("Word2:", wordPtr)
    fmt.Println("numb:", *numPtr)
    fmt.Println("numb2", numPtr)
    fmt.Println("switchflag", *boolPtr)
    fmt.Println("switchflag2", boolPtr)
    fmt.Println("svar:", svar)
    fmt.Println("svar2", &svar)
    fmt.Println("svar3", *svar) //<-- This won't work...
    fmt.Println("tail:", flag.Args())

}

My question is, why do I get the value of the other pointers if I dereference it (like *wordPtr etc), whereas if I pass wordPtr in, I get the memory address, but with svar, I have to pass in svar to get the value, and &svar gets me the memory address?

Looking at the documentation here https://golang.org/pkg/flag/, it says that you pass in a variable to store the flag (presumably a variable that is already created?), but I still don't understand why I have to do something different to it to get the value, when compared with other variables.

This is the result of me running it with passing in some commands:

➜  Documents go run main.go -number 42 -switchflag -svar testtringvalue
Word: stringvalue
Word2: 0xc42005c1e0
numb: 42
numb2 0xc4200160a0
switchflag true
switchflag2 0xc4200160a8
svar: testtringvalue
svar2 0xc42005c1f0
tail: []

Any help is appreciated. Also, if I've got any understanding of it wrong, please let me know.

Cheers.

Answer 1

Well this is fairly simple, you are trying to dereference a value instead of pointer.

var svar string is not a pointer, but a value.

fmt.Println("svar3", svar) is correct use in this case

Don't worry about about use of StringVar as ...Var(&svar, "sv... means that you are passing address of svar not a value.