How to convert a 'string pointer' to a string in Golang?

Question

Is it possible to get the string value from a pointer to a string?

I am using the goopt package to handle flag parsing and the package returns *string only. I want to use these values to call a function in a map.

Example

var strPointer = new(string)
*strPointer = "string"

functions := map[string]func() {
    "string": func(){
        fmt.Println("works")
    },
}  

//Do something to get the string value

functions[strPointerValue]()

returns

./prog.go:17:14: cannot use strPointer (type *string) 
as type string in map index

OneOfOne · Accepted Answer · 2014-10-21 18:46:14Z

156

Dereference the pointer:

strPointerValue := *strPointer

answered Oct 21, 2014 at 18:46

OneOfOne

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3 Comments

Matteo Over a year ago

that's correct, however if the pointer string is nil you will have a runtime error

ram4nd Over a year ago

What would be a better solution then?

Archie Yalakki Over a year ago

@ram4nd if strPointer != nil { strPointerValue := *strPointer }

Ozan · Accepted Answer · 2020-07-08 08:19:43Z

27

A simple function that first checks if the string pointer is nil would prevent runtime errors:

func DerefString(s *string) string {
    if s != nil {
        return *s
    }

    return ""
}

answered Jul 8, 2020 at 8:19

Ozan

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Comments

Spencer Connaughton · Accepted Answer · 2022-09-06 19:06:37Z

7

Generic https://stackoverflow.com/a/62790458/1079543 :

func SafeDeref[T any](p *T) T {
    if p == nil {
        var v T
        return v
    }
    return *p
}

answered Sep 6, 2022 at 19:06

Spencer Connaughton

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