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

score 148 · Accepted Answer · answered Oct 21 '14 at 18:46

148

Dereference the pointer:

strPointerValue := *strPointer

answered Oct 21 '14 at 18:46

OneOfOne

95,033
20
184
185

12

that's correct, however if the pointer string is `nil` you will have a runtime error – Matteo Nov 12 '19 at 00:16
2

What would be a better solution then? – ram4nd Feb 17 '20 at 14:45
2

@ram4nd if strPointer != nil { strPointerValue := *strPointer } – Archie Yalakki Feb 24 '21 at 10:42

score 25 · Answer 2 · answered Jul 08 '20 at 08:19

25

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 08 '20 at 08:19

Ozan

331
4
4

score 3 · Answer 3 · answered Sep 06 '22 at 19:06

3

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 06 '22 at 19:06

Spencer Connaughton

892
6
21

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

3 Answers3